--- src/Tier.py 2006-12-14 11:27:49.000000000 -0800
+++ src/.#Tier.py.1.38  2006-12-13 17:32:07.000000000 -0800
@@ -507,7 +507,7 @@
       layer = event.getLayer()
       perk = task.getPerk()
       task_data = event.getDataForTask()
-      if not perk.preExecute(layer):
+      if not perk or not perk.preExecute(layer):
         return
       # execute that Task
       self._executeTask(task, None, layer, task_data, True)