Fix: The check if upload_max_filesize or post_max_size is 0 fails if only one of them is 0.

$upload_max_filesize and $post_max_size need to be casted to (int) to match "=== 0"
Merge pull request #3688 from roha4000/fix_upload_max_filesize

upload_max_filesize = 0 not possible if post_max_size is not 0