Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/ui/gtk3/panes/installedpane.py", line 279, in _row_visibility_func
    row = model.get_value(it, col)
  File "/usr/lib/python2.7/dist-packages/gi/types.py", line 43, in function
    return info.invoke(*args, **kwargs)
TypeError: unknown type (null)