probable bug in @on_trait_change with delegated lists

> I'm not sure how to proceed with this one. I updated to the latest
> trunk version of /TUI. It has been a while (read months) since my last update. 
> My app, which was working fine, is now broken. 

I was able to do some isolation and I managed to locate the source of the
traceback. In either my handler or object code if I put the following block
in my code, I get the error.

@on_trait_change('info:object:root:sub_contexts*') 
def tree_handler_sub_contexts(self, object, name, new): 
  print "fired tree_handler_sub_contexts", object, name, new

I get the traceback:

--------------------------------------------------------
fired tree_handler_sub_contexts <elm_objects.ExtendableContext object at 0x02B63
870> sub_contexts <enthought.traits.trait_handlers.TraitListEvent object at 0x02
D3DF30>
Exception occurred in traits notification handler.
Please check the log file for details.
Exception occurred in traits notification handler for object: <elm_objects.Exten
dableContext object at 0x02B63870>, trait: sub_contexts, old value: <undefined>,
 new value: <enthought.traits.trait_handlers.TraitListEvent object at 0x02D3DF30
>
Traceback (most recent call last):
  File "d:\enthought\checkouts\traits_3.0.0b1\enthought\traits\trait_notifiers.p
y", line 580, in rebind_call_4
    object, trait_name, old, new )
  File "d:\enthought\checkouts\traits_3.0.0b1\enthought\traits\trait_notifiers.p
y", line 418, in dispatch
    handler( *args )
  File "d:\enthought\checkouts\traits_3.0.0b1\enthought\traits\traits_listener.p
y", line 511, in handle_list
    for obj in old:
TypeError: '_Undefined' object is not iterable
--------------------------------------------------------

if I change the the code block to (get rid of the star):

@on_trait_change('info:object:root:sub_contexts') 
def tree_handler_sub_contexts(self, object, name, new): 
  print "fired tree_handler_sub_contexts", object, name, new

then I don't get the traceback. Of course the handler only fires on depth
one below the root. 

The subtlety is that in my code sub_contexts are delegated through a
LogicElement via:
context.sub_contexts = context.logic_element.sub_contexts

I have a similar version of the code that does not use delegation and does not
show the bug. It would seem that the bug is in the combination of catching 
changes to a delegated list using the '*' pattern.

D