[Pushed] Being "hidden" isn't so hidden if you know where to look

[Devilshakerz]

Adding

	if($sort_field == 'u.lastactive' && $mybb->usergroup['canviewwolinvis'] == 0)
	{
		$sort_field = "u.invisible ASC, CASE WHEN u.invisible = 1 THEN u.regdate ELSE u.lastactive END";
	}

at https://github.com/mybb/mybb/blob/mybb_1...t.php#L154 would place invisible users at the end, sorted by registration date, unless the current user has proper permissions.