setting a milestone for several bugs gives a system error

[Robert Collins]

I went to ../malone/products/bazaar, chose several bugs and selected assign-to-milestone Future.
Then it gave me a system error, and this URL in my status bar.
https://launchpad.ubuntu.com/malone/products/bazaar?searchtext=&advanced=&task=212&task=210&task=209&task=197&assign_to_milestone=Assign+to+Milestone&milestone=future&status=10&status=20&assignee=all

[Robert Collins (lifeless)]

still occuring, and also occurs for a single bug

[Stuart Bishop (stub)]

Traceback is as follows:

  File "/home/launchpad/dists/launchpad/lib/canonical/launchpad/browser/editview.py", line 94, in update
    self.request))
  File "/home/launchpad/dists/launchpad/lib/zope/event/__init__.py", line 23, in notify
    subscriber(event)
  File "/home/launchpad/dists/launchpad/lib/zope/app/event/dispatching.py", line 65, in dispatch
    for ignored in subscribers(event, None):
  File "/home/launchpad/dists/launchpad/lib/zope/component/__init__.py", line 190, in subscribers
    return adapters.subscribers(objects, interface)
  File "/home/launchpad/dists/launchpad/lib/zope/interface/adapter.py", line 467, in subscribers
    return [subscription(*objects) for subscription in subscriptions]
  File "/home/launchpad/dists/launchpad/lib/zope/app/event/objectevent.py", line 76, in objectEventNotify
    adapters = subscribers((event.object, event), None)
  File "/home/launchpad/dists/launchpad/lib/zope/component/__init__.py", line 190, in subscribers
    return adapters.subscribers(objects, interface)
  File "/home/launchpad/dists/launchpad/lib/zope/interface/adapter.py", line 467, in subscribers
    return [subscription(*objects) for subscription in subscriptions]
  File "/home/launchpad/dists/launchpad/lib/canonical/launchpad/mailnotification.py", line 427, in notify_bugtask_edited
    bugtask_delta = get_task_delta(
  File "/home/launchpad/dists/launchpad/lib/canonical/launchpad/mailnotification.py", line 316, in get_task_delta
    return BugTaskDelta(**changes)
TypeError: __init__() got an unexpected keyword argument 'milestone'