diff -r 08834607d4db -r 7349b09373a0 gui/graph_displayer_canvas-event.cc
--- a/gui/graph_displayer_canvas-event.cc	Thu Feb 02 13:43:01 2006 +0000
+++ b/gui/graph_displayer_canvas-event.cc	Thu Feb 02 15:44:45 2006 +0000
@@ -554,6 +554,9 @@
 	    }
 	}
 
+      // return if the clicked object is neither an edge nor a node
+      if (active_edge == INVALID) return false;
+      
       //recolor activated item
       if(active_item)
 	{
@@ -596,7 +599,7 @@
 		  deleteItem(active_node);
 		}
 	      //a simple edge was chosen
-	      else
+	      else if (active_edge != INVALID)
 		{
 		  deleteItem(active_edge);
 		}
@@ -608,7 +611,7 @@
 		{
 		  *active_item << Gnome::Canvas::Properties::fill_color("blue");
 		}
-	      else
+	      else if (active_edge != INVALID)
 		{
 		  *active_item << Gnome::Canvas::Properties::fill_color("green");
 		}