woo2iiko default value for teminal's select

woo-to-iiko.php

add_filter('iiko_checkout_fields', function ($fields){
    $fields['delivery_terminal']['default'] = '';
    $fields['delivery_terminal']['options'] = [''=>''] + $fields['delivery_terminal']['options'];
    return $fields;
}, 10, 1 );

add_action( 'woocommerce_after_checkout_validation', function ($data, \WP_Error $errors) {
            if(isset($data['billing_delivery_terminal']) && empty($data['billing_delivery_terminal'])){
                $errors->add('iiko_terminal', __('Please select the terminal', 'iiko'));
            }
            return $data;
}, 10, 2);