Error on create ticket after implement PrivateTicketsPlugin (TracHoursPlugin installed)

[wandi.ms@…]

After implement PrivateTicketsPlugin, whenever i create a ticket raise error message like this :

 Trac detected an internal error:

TypeError: argument of type 'NoneType' is not iterable


Python Traceback
Most recent call last:

File "/usr/lib/python2.6/dist-packages/trac/web/main.py", line 444, in _dispatch_request
  dispatcher.dispatch(req)
File "/usr/lib/python2.6/dist-packages/trac/web/main.py", line 205, in dispatch
  resp = chosen_handler.process_request(req)
File "/usr/lib/python2.6/dist-packages/trac/ticket/web_ui.py", line 183, in process_request
  return self._process_newticket_request(req)
File "/usr/lib/python2.6/dist-packages/trac/ticket/web_ui.py", line 400, in _process_newticket_request
  valid = self._validate_ticket(req, ticket)
File "/usr/lib/python2.6/dist-packages/trac/ticket/web_ui.py", line 970, in _validate_ticket
  for field, message in manipulator.validate_ticket(req, ticket):
File "/usr/local/lib/python2.6/dist-packages/TracHoursPlugin-0.5.2-py2.6.egg/trachours/ticket.py", line 45, in validate_ticket
  can_add_hours = PermissionSystem(self.env).check_permission('TICKET_ADD_HOURS', user)
File "/usr/lib/python2.6/dist-packages/trac/perm.py", line 425, in check_permission
  perm)
File "build/bdist.linux-i686/egg/privatetickets/policy.py", line 34, in check_permission

[rjollos]

Duplicate of #5825, which I am currently working to resolve.