Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/ui/gtk3/widgets/apptreeview.py", line 519, in _on_net_state_changed
    self._update_selected_row(self, tr)
  File "/usr/share/software-center/softwarecenter/ui/gtk3/widgets/apptreeview.py", line 276, in _update_selected_row
    if self.appmodel.is_installed(app):
  File "/usr/share/software-center/softwarecenter/ui/gtk3/models/appstore2.py", line 111, in is_installed
    if doc.installed is None:
AttributeError: CategoryRowReference instance has no attribute 'installed'