--- gtk+-2.4.4/gtk/gtktreeview.c~	2004-03-15 04:40:03.000000000 +0100
+++ gtk+-2.4.4/gtk/gtktreeview.c	2004-08-10 21:20:39.435484664 +0200
@@ -5570,7 +5570,7 @@
 
   di = get_info (tree_view);
 
-  if (di == NULL)
+  if (di == NULL || !di->source_set)
     goto out;
 
   if (tree_view->priv->pressed_button < 0)