[BUG] Phalcon\Forms\Form::getMessages() produces PHP error if form is valid.

[temuri416]

Call to Phalcon\Forms\Form::getMessages() fails if there are no form validation errors.

Phalcon\Forms\Form::getMessages() in the code below would raise PHP E_ERROR "The argument is not iterable()":

$form = new Phalcon\Forms\Form;
$form->add(new Phalcon\Forms\Element\Text('name'));
$form->isValid([
    'name' => 'John',
]);
$form->getMessages();

If form fails validation $form->getMessages() works as expected.

Implement bug fix.

I am on Phalcon 1.3.0.

Thanks!