File upload is broken when submitting a form

...without selecting a file in Laravel 5! My tests revealed that with this tweek the problem described at this issue are resolved: laravel/framework#6189 

...in Symfony on the FileBag.php file, convertFileInformation() method returns NULL if no files was selected on the upload. In this case "FileBag->set('image', NULL)" receives NULL, and that is what is dispatching a throw!

I don't make unit tests, but this will no more break my code flow. I'm not sure if this is the real deal! If someone could look deeper into the problem, I appreciated! 

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | 
| License       | MIT
| Doc PR        |