diff -r 3b92f0b96d31 -r 549c413cefce graphics/SFC_Objects.py
--- a/graphics/SFC_Objects.py	Mon Sep 08 13:56:34 2008 +0200
+++ b/graphics/SFC_Objects.py	Mon Sep 08 16:56:48 2008 +0200
@@ -84,11 +84,13 @@
         if self.Parent.Debug:
             spreading = self.Value
             if spreading and not self.PreviousSpreading:
-                self.Output.SpreadCurrent(True)
+                if self.Output is not None:
+                    self.Output.SpreadCurrent(True)
                 if self.Action is not None:
                     self.Action.SpreadCurrent(True)
             elif not spreading and self.PreviousSpreading:
-                self.Output.SpreadCurrent(False)
+                if self.Output is not None:
+                    self.Output.SpreadCurrent(False)
                 if self.Action is not None:
                     self.Action.SpreadCurrent(False)
             self.PreviousSpreading = spreading