Workflow cleanup: avoid errors when there is no action type

product/ERP5Workflow/Document/Transition.py

@@ -86,10 +86,10 @@ class Transition(IdAsReferenceMixin("transition_", "prefix"), XMLObject,
   security.declareProtected(Permissions.AccessContentsInformation,
                             'getActionType')
   def getActionType(self):
-    prefix_length = len('action_type/')
-    action_type_list = [path[prefix_length:] for path in self.getCategoryList()
-                        if path.startswith('action_type/')]
-    return action_type_list[0]
+    for path in self.getCategoryList():
+      if path.startswith('action_type/'):
+        return path[12:] # 12 is len('action_type/')
+    return None
 
   security.declareProtected(Permissions.AccessContentsInformation,
                             'getBeforeScriptList')