I'm receiving a very similar error when I try to do a search on an account that is not an administrative account.

Fatal error: Call to a member function getGUID() on a non-object in .../mod/form/views/default/form/search_results.php on line 26

I've been messing around with it for a while and I haven't been able to find anything to allow non-admin or even non-logged in people to be able to use the search.