Tag and contact type searches stopped working after upgrade to 4.6.13

After upgrading from 4.6.11 to 4.6.13, I found that searching on tags or contact types had stopped working - and because of this, any smart groups involving tags stopped working too. After some debugging, I tracked down the problem to the legacyConvertFormValues function.

I got the search working as normal again by commenting out line 1483 in CRM/Contact/BAO/Query.php:
//self::legacyConvertFormValues($id, $values);

I still can't save searches as smartgroups if they include tags though.