Fix ->validationErrors->count() when the object is null

Hi... in the **src/LaravelBook/Ardent/Ardent.php** line **541** i've found an issue: The `$this->validationErrors->count()` causes an error because `validationErrors` is null and does not retrive the `count()` method.

See this [Screenshot](http://i.imgur.com/AnI1t8u.png)

Then a single check if it's null, solve it... I do know how the object is null in my case, but here is my suggestion in this pull request.

Sorry about my poor english!


I think it would look cleaner if these two conditions were merged.

`$this->validationErrors = new MessageBag;` is executed in both cases anyway.