Author: Davo Smith
MDL-31112 Repository upload - check for completely null files (likely to be folders uploaded by mistake via drag and drop)
http://git.moodle.org/gw?p=moodle.git;a=commit;h=87ed3a5c39f11ae0f6e1ad074f92e22e362b70e8
http://github.com/moodle/moodle/commit/87ed3a5c39f11ae0f6e1ad074f92e22e362b70e8
+ 2.3 en [upload_error_invalid_file,repository_upload]