Catchable fatal error: Argument 1 passed to Zend\Form\Element\Select::setValueOptions() must be of the type array, null given, called in C:\Users\Nilton\Google Drive\localhost\AutoEscola\src\module\Aluno\src\Aluno\Form\Contrato.php on line 42

AlunoTable.php

<?php

namespace Aluno\Model;

use Zend\Db\TableGateway\TableGateway;
use \Exception;

// import for fetchPaginator
use Zend\Db\Sql\Select,
    Zend\Db\ResultSet\HydratingResultSet,
    Zend\Stdlib\Hydrator\Reflection,
    Zend\Paginator\Adapter\DbSelect,
    Zend\Paginator\Paginator;

class AlunoTable {
    protected $tableGateway;
    
    public function __construct(TableGateway $tableGateway) {       
        $this->tableGateway = $tableGateway;
    }
    
    public function fetchAll(){
        return $this->tableGateway->select();
    }
    
    public function fetchPairs(){
        
        $todos = $this->fetchAll();
        
        $array = array();
        
         
        foreach($todos as $aluno){
            $array[$aluno->id] = $aluno->nome;
        }
        return $array;
    }
    
    public function find($id){
        $id = (int)$id;
        $rowset = $this->tableGateway->select(array('id' => $id));
        $row = $rowset->current();
        if(!$row){
             throw new Exception("Não foi encontrado aluno de id = {$id}");
        }
        return $row;
    }
    
     public function save(Aluno $aluno)
    {
        $timeNow = new \DateTime();
 
        $data = [
            'nome'                  => $aluno->nome,
            'email'                 => $aluno->email,
            'sexo'                  => $aluno->sexo,
            'telefone'              => $aluno->telefone,
            'telefone2'             => $aluno->telefone2,
            'data_nascimento'       => $aluno->data_nascimento,
            'data_cadastro'         => $timeNow->format('Y-m-d H:i:s'), 
            'data_alteracao'        => $timeNow->format('Y-m-d H:i:s'), # data de criação igual a de atualização 
        ];
 
        return $this->tableGateway->insert($data);
    }
    
     public function update(Aluno $aluno)
    {
        $timeNow = new \DateTime();
 
        $data = [
            'nome'                  => $aluno->nome,
            'email'                 => $aluno->email,
            'sexo'                  => $aluno->sexo,
            'telefone'              => $aluno->telefone,
            'telefone2'             => $aluno->telefone2,
            'data_nascimento'       => $aluno->data_nascimento,
            'data_alteracao'        => $timeNow->format('Y-m-d H:i:s'), # data de criação igual a de atualização 
        ];
 
        $id = (int) $aluno->id;
        if ($this->find($id)) {
            $this->tableGateway->update($data, array('id' => $id));
        } else {
            throw new Exception("Aluno #{$id} inexistente");
        }
    }
    
    public function delete($id)
    {
        $this->tableGateway->delete(array('id' => (int) $id));
    }
    
    
    

    /**
     * Localizar itens por paginação
     * 
     * @param type $pagina
     * @param type $itensPagina
     * @param type $ordem
     * @param type $like
     * @param type $itensPaginacao
     * @return type Paginator
     */
    public function fetchPaginator($pagina = 1, $itensPagina = 10, $ordem = 'nome ASC', $like = null, $itensPaginacao = 5) 
    {

        $select = (new Select('alunos'))->order($ordem);

        if (isset($like)) {
            $select
                    ->where
                    ->like('id', "%{$like}%")
                    ->or
                    ->like('nome', "%{$like}%")
                    ->or
                    ->like('telefone', "%{$like}%")
                    ->or
                    ->like('data_cadastro', "%{$like}%")
                    ->or
            ;
        }


        $resultSet = new HydratingResultSet(new Reflection(), new Aluno());


        $paginatorAdapter = new DbSelect(
            $select,
            $this->tableGateway->getAdapter(),
            $resultSet
        );

        return (new Paginator($paginatorAdapter))
                // pagina a ser buscada
                ->setCurrentPageNumber((int) $pagina)
                // quantidade de itens na página
                ->setItemCountPerPage((int) $itensPagina)
                ->setPageRange((int) $itensPaginacao);
    }


}

Contrato.php

<?php

namespace Aluno\Form;

use Zend\Form\Form,
    Zend\Form\Element\Select,
    Zend\Form\Element;

class Contrato extends Form{
    
    protected $alunos;
    
    public function __construct($name = null, array $alunos = null)
    {
        parent::__construct('contrato');
        
        $this->alunos = $alunos;
        
        $this->setInputFilter(new ContratoFilter);
        
        $this->setAttributes(array(
            'method'    => 'post',
            'class'     => 'form-horizontal',
        ));
 
 
        $this->add(array(
            'type' => 'Hidden',
            'name' => 'id',
        ));
 
           
        $aluno = new Select();
        $aluno->setName("aluno_id")
               ->setAttributes(array(
                   'class' => 'form-control',
                   'id'            => 'aluno_id',
                   'placeholder'   => 'Alunos',
                   'required'      => true,
                   ))
              
               ->setValueOptions($this->alunos)
               ->setEmptyOption('Insira um aluno')
               ->setDisableInArrayValidator(true);
        
        $this->add($aluno);
        
        
        
        $this->add(array(
            'name' => 'valor',
            'options' => array(
               'type' => 'text',
                'label' => 'Valor', 
            ),
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'nome',
                'placeholder'   => 'Valor',
                'required'      => true,
                ),
        ));
        
        $this->add(array(
            'type' => 'text',
            'name' => 'quant_meses',
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'quant_meses',
                'placeholder'   => 'Quantidade Meses',
                'required'      => true,
            ),
        ));
        

        $this->add(array(
            'type' => 'Date',
            'name' => 'data_inicio',
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'data_inicio',
                'placeholder'   => 'Data de Início',
                'required'      => true,
            ),
        ));
        
        $this->add(array(
            'type' => 'Date',
            'name' => 'data_fim',
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'data_fim',
                'placeholder'   => 'Data de Fim',
                'required'      => true,
            ),
        ));
 

        // elemento para evitar ataques Cross-Site Request Forgery
        $this->add(new Element\Csrf('security'));
    }
 
}

ContratoController.php

 // coloquei só a action Novo e Adicionar (que é a action que o formulário está enviando)
 
 public function novoAction()
    {                         
        $alunos = $this->getServiceLocator()->get("ModelAluno")->fetchPairs();
        return ['form' => new $this->form(null, $alunos)];
    }
 
 public function adicionarAction()
    {
         $request = $this->getRequest();
 
        if ($request->isPost()) {
            $form = new $this->form();
            $form->setData($request->getPost());
            $model = new $this->model();
        if ($form->isValid()) {
            
            $model->exchangeArray($form->getData());
            $this->getServiceTable()->save($model);
            
            $this->flashMessenger()->addSuccessMessage("Cadastro criado com sucesso");
            return $this->redirect()->toRoute($this->route);
        } else {
            $this->flashMessenger()->addErrorMessage("Erro ao criar cadastro");
           return (new ViewModel())
                            ->setVariable('form', $form)
                            ->setTemplate($this->caminhoViews.'novo');
        }
    }

Formulário.contrato.php

<?php

namespace Aluno\Form;

use Zend\Form\Form,
    Zend\Form\Element\Select,
    Zend\Form\Element;

class Contrato extends Form{
    
    protected $alunos;
    
    public function __construct($name = null, array $alunos = null)
    {
        parent::__construct('contrato');
        
        $this->alunos = $alunos;
        
        $this->setInputFilter(new ContratoFilter);
        
        $this->setAttributes(array(
            'method'    => 'post',
            'class'     => 'form-horizontal',
        ));
 
 
        $this->add(array(
            'type' => 'Hidden',
            'name' => 'id',
        ));
 
           
        $aluno = new Select();
        $aluno->setName("aluno_id")
               ->setAttributes(array(
                   'class' => 'form-control',
                   'id'            => 'aluno_id',
                   'placeholder'   => 'Alunos',
                   'required'      => true,
                   ))
              
               ->setValueOptions($this->alunos)
               ->setEmptyOption('Insira um aluno')
               ->setDisableInArrayValidator(true);
        
        $this->add($aluno);
        
        
        
        $this->add(array(
            'name' => 'valor',
            'options' => array(
               'type' => 'text',
                'label' => 'Valor', 
            ),
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'nome',
                'placeholder'   => 'Valor',
                'required'      => true,
                ),
        ));
        
        $this->add(array(
            'type' => 'text',
            'name' => 'quant_meses',
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'quant_meses',
                'placeholder'   => 'Quantidade Meses',
                'required'      => true,
            ),
        ));
        

        $this->add(array(
            'type' => 'Date',
            'name' => 'data_inicio',
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'data_inicio',
                'placeholder'   => 'Data de Início',
                'required'      => true,
            ),
        ));
        
        $this->add(array(
            'type' => 'Date',
            'name' => 'data_fim',
            'attributes' => array(
                'class'         => 'form-control',
                'id'            => 'data_fim',
                'placeholder'   => 'Data de Fim',
                'required'      => true,
            ),
        ));
 

        // elemento para evitar ataques Cross-Site Request Forgery
        $this->add(new Element\Csrf('security'));
    }
 
}

View.novo.phtml

<div class="panel panel-primary">
    <div class="panel-heading">
        <div class="panel-title">
            Novo Contrato           
        </div>
    </div>
    <?php
    $form = $this->form;
    $form->setAttribute('action', $this->url('contratos', array('action' => 'adicionar')));
    $form->prepare();
    echo $this->form()->openTag($form);
    ?>
    <form class="form-horizontal" role="form" method="POST" action="<?php echo $this->url('contratos', array('action' => 'adicionar')); ?>">
        <div class="panel-body">
            
            <div class="form-group">
                <label for="aluno_id" class="col-lg-3 col-md-3 control-label">Aluno:</label>
                <div class="col-lg-9  col-md-9">
                    <?php echo $this->formRow($form->get('aluno_id')); 
                        // renderiza elemento de erro
                        echo $this->formElementErrors()
                        ->setMessageOpenFormat('<small class="text-danger">')
                        ->setMessageSeparatorString('</small><br/><small class="text-danger">')
                        ->setMessageCloseString('</small>')
                        ->render($form->get('aluno_id'));
                    ?>
                </div>
            </div>
            
            
            <div class="form-group">
                <label for="valor" class="col-lg-3 col-md-3 control-label">Valor:</label>
                <div class="col-lg-9 col-md-9">
                    <?php echo $this->formInput($form->get('valor')); 
                        // renderiza elemento de erro
                        echo $this->formElementErrors()
                        ->setMessageOpenFormat('<small class="text-danger">')
                        ->setMessageSeparatorString('</small><br/><small class="text-danger">')
                        ->setMessageCloseString('</small>')
                        ->render($form->get('valor'));
                    ?>
                    
                </div>
            </div>
            
            <div class="form-group">
                <label for="quant_meses" class="col-lg-3 col-md-3 control-label">Quantidade de Meses:</label>
                <div class="col-lg-9  col-md-9">
                    <?php echo $this->formInput($form->get('quant_meses'));
                        // renderiza elemento de erro
                        echo $this->formElementErrors()
                        ->setMessageOpenFormat('<small class="text-danger">')
                        ->setMessageSeparatorString('</small><br/><small class="text-danger">')
                        ->setMessageCloseString('</small>')
                        ->render($form->get('quant_meses'));
                    ?>
                </div>
            </div>
            
            
            <div class="form-group">
                <label for="data_inicio" class="col-lg-3 col-md-3 control-label">Data Inicial:</label>
                <div class="col-lg-9  col-md-9">
                    <?php echo $this->formInput($form->get('data_inicio')); 
                        // renderiza elemento de erro
                        echo $this->formElementErrors()
                        ->setMessageOpenFormat('<small class="text-danger">')
                        ->setMessageSeparatorString('</small><br/><small class="text-danger">')
                        ->setMessageCloseString('</small>')
                        ->render($form->get('data_inicio'));
                    ?>
                </div>
            </div>
            
            
            <div class="form-group">
                <label for="data_fim" class="col-lg-3 col-md-3 control-label">Data Final:</label>
                <div class="col-lg-9  col-md-9">
                    <?php echo $this->formInput($form->get('data_fim')); 
                        // renderiza elemento de erro
                        echo $this->formElementErrors()
                        ->setMessageOpenFormat('<small class="text-danger">')
                        ->setMessageSeparatorString('</small><br/><small class="text-danger">')
                        ->setMessageCloseString('</small>')
                        ->render($form->get('data_fim'));
                    ?>
                </div>
            </div>
 
        </div>
        <div class="panel-footer">
            <?php
            echo $this->formHidden($form->get('id'));
            echo $this->formElement($form->get('security')); 
            ?>
            <button type="submit" class="btn btn-primary">Salvar Contato</button>
            <a href="<?php echo $this->url('contratos'); ?>" class="btn btn-default">Voltar</a>
        </div>
         <?php echo $this->form()->closeTag() ?>
</div>

Erro na linha 42 do Contrato.php: ->setValueOptions($this->alunos) , o array $this->alunos vem do método fetchPairs() na linha 26 do AlunoTable.php

Acho que o erro está no fetchPais() , estou criando o array certo?