Yeah, that's a minor issue with that version. You can fix it by editing the code in packages/vbforum/item, in socialgroupmessage.php and socialgroupdiscussion.php. In both cases you want to find this:
Code:
protected function getLoadQuery($required_query = null, $force_rebuild = false)
and add the '= null' (in red above).
If you have php 5.4 or later you could also upgrade to vb4.2.3 (but of course there's always a little risk with upgrading).