argument of type 'NoneType' is not iterable

  File "/Users/rae/work/osaf/chandler/chandler/util/task.py", line 65, in __threadStart
    result = self.run()
  File "/Users/rae/work/osaf/chandler/chandler/application/dialogs/PublishCollection.py", line 480, in run
    activity=task.activity)
  File "/Users/rae/work/osaf/chandler/chandler/parcels/osaf/sharing/__init__.py", line 486, in publish
    supportsTickets = handle.blockUntil(resource.supportsTickets)
  File "/Users/rae/work/osaf/chandler/chandler/parcels/osaf/sharing/WebDAV.py", line 84, in blockUntil
    return zanshin.util.blockUntil(callable, *args, **keywds)
  File "/Users/rae/work/osaf/chandler/chandler/release/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/zanshin/util.py", line 208, in blockUntil
    res.raiseException()
  File "/Users/rae/work/osaf/chandler/chandler/release/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/twisted/python/failure.py", line 259, in raiseException
    raise self.type, self.value, self.tb
<type 'exceptions.TypeError'> argument of type 'NoneType' is not iterable