Index: smartqueue.module
===================================================================
--- smartqueue.module	(revision 128)
+++ smartqueue.module	(working copy)
@@ -41,7 +41,7 @@
   );
 
 
-  if ($queue->qid) {
+  if (!empty($queue->qid)) {
     $form['placeholder']['vocabularies']['#disabled'] = TRUE;
     $form['placeholder']['vocabularies']['#default_value'] = explode('-', $queue->reference);
   }