Index: category.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/category/category.inc,v
retrieving revision 1.42.2.13
diff -u -r1.42.2.13 category.inc
--- category.inc	10 Jul 2006 09:02:10 -0000	1.42.2.13
+++ category.inc	18 Jul 2006 09:47:10 -0000
@@ -39,7 +39,9 @@
     }
   }
 
-  return $categories[$cid];
+  if ($categories[$cid]) {
+    return drupal_clone($categories[$cid]);
+  }
 }
 
 /**