Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 576, in msg_reply_handler
    reply_handler(*message.get_args_list(**get_args_opts))
  File "/usr/lib/python2.6/dist-packages/aptdaemon/client.py", line 274, in sync_properties
    reply_handler(self)
  File "/usr/lib/python2.6/dist-packages/aptdaemon/client.py", line 534, in reply
    reply_handler(trans)
  File "/usr/share/software-center/softwarecenter/backend/aptd.py", line 76, in <lambda>
    None)
  File "/usr/share/software-center/softwarecenter/backend/aptd.py", line 181, in _run_transaction
    error_handler=self._on_trans_error)
  File "/usr/lib/python2.6/dist-packages/aptdaemon/client.py", line 366, in set_meta_data
    error_handler=error_handler)
  File "/usr/lib/pymodules/python2.6/dbus/proxies.py", line 132, in __call__
    **keywords)
  File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 556, in call_async
    message.append(signature=signature, *args)
TypeError: Don't know how which D-Bus type to use to encode type "NoneType"