generate_text_for_storage() kills the uid if there is no bitfield, posting.php (parse_message) doesn't

As of phpBB 3.2, all the messages posted via posting.php have the uid field set, even if the bitfield is empty.

generate_text_for_storage() kills the uid if there is no bitfield (see includes\functions_content.php#722).

As far as I can tell, the missing uid causes some compatibility problem with Tapatalk. I think the uid must be preserved or, at least, both functions should work the same way.