[BUG] [CRASH] Segmentation Fault in Phalcon\Validation::bind()

Similar to #741 — when bind() is passed invalid parameters, segmentation fault happens.

Test case:
```php
<?php
$v = new Phalcon\Validation;
try {
        $v->bind(0, 0); // segfaults here
}
catch (Exception $e) {
        echo "Exception caught!\n";
}
```