[5.0] File upload is broken when submitting a form without selecting a file.

"I open a pull request here too, because I dont know the right place to put it. if is here in laravel framework, or there in the illuminate repository. https://github.com/illuminate/http/pull/14"

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: https://github.com/laravel/framework/issues/6189

Credits to @Marwelln

This resolves a problem that occours in Symfony on the FileBag.php file, convertFileInformation() method. It receaves a empty array file and than 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 in Symfony.

I misunderstood the problem, and try attempt to do a pull request on symfony, but it was denied: https://github.com/symfony/symfony/pull/12486

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!
Please use: `$file !== null`. No yoda conditions please.