FOF: Don't overwrite values in the db when fields are not within the form

gistfile1.php

class whatModelever extends FOFModel
{

.....

	/**
	 * This method runs before the $data is saved to the $table. Return false to
	 * stop saving.
	 *
	 * @param   array     &$data   The data to save
	 * @param   FOFTable  &$table  The table to save the data to
	 *
	 * @return  boolean  Return false to prevent saving, true to allow it
	 */
	protected function onBeforeSave(&$data, &$table)
	{
		$result = parent::onBeforeSave($data, $table);

		/*
			next lines make sure that not in a form existing fields are
			are not set to null
		 */
		if ($result && !$this->_isNewRecord)
		{
			// Get the form if there is any
			$form = $this->getForm($data, false);

			if ($form instanceof FOFForm)
			{
				$formdata = $this->input->getData();
				$key = $table->getKeyName();
				$SavedRecord = $this->getTable();
				$SavedRecord->load($table->$key);

				// get the fields
				$fieldset = $form->getFieldset();

				foreach ($fieldset as $nfield => $fldset)
				{
					if (!array_key_exists($nfield, $formdata))
					{
						$oldValue = $SavedRecord->$nfield;
						$table->$nfield = $oldValue;
						$data[$nfield]  = $oldValue;

					}
				}
			}
		}

		return true;
	}
.....

}