Traceback (most recent call last):
  File "/usr/bin/software-center", line 91, in <module>
    app.run(args)
  File "/usr/share/software-center/softwarecenter/app.py", line 1064, in run
    self.show_available_packages(args)
  File "/usr/share/software-center/softwarecenter/app.py", line 995, in show_available_packages
    self.installed_pane.show_app(app)
  File "/usr/share/software-center/softwarecenter/view/installedpane.py", line 208, in show_app
    self.app_details.show_app(app)
  File "/usr/share/software-center/softwarecenter/view/appdetailsview_gtk.py", line 1494, in show_app
    self._update_page(self.app_details)
  File "/usr/share/software-center/softwarecenter/view/appdetailsview_gtk.py", line 1377, in _update_page
    self._configure_where_is_it()
  File "/usr/share/software-center/softwarecenter/view/appdetailsview_gtk.py", line 1426, in _configure_where_is_it
    if os.path.exists(p):
  File "/usr/lib/python2.6/genericpath.py", line 18, in exists
    st = os.stat(path)
TypeError: coercing to Unicode: need string or buffer, NoneType found