Traceback (most recent call last):
  File "/var/lib/python-support/python2.5/gpodder/gui.py", line 1192, in on_treeChannels_cursor_changed
    self.updateTreeView()
  File "/var/lib/python-support/python2.5/gpodder/gui.py", line 621, in updateTreeView
    self.treeAvailable.set_model( self.active_channel.tree_model)
AttributeError: 'NoneType' object has no attribute 'tree_model'