Handle ::find(NULL) on Group and User models.

application/modules/auth/models/GroupModel.php

@@ -225,7 +225,7 @@ class Auth_GroupModel extends Unl_Model
             }
             $select->where('parentGroup IN(?)', $group->getId());
         } else {
-            $select->where('parentGroup = ?', $group->getId());
+            $select->where($db->quoteInto('parentGroup = ?', $group->getId()));
         }
         
         $records = $select->query()->fetchAll();