Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/ui/gtk3/panes/viewswitcher.py", line 151, in config_view
    pane = vm.set_active_view(view_id)
  File "/usr/share/software-center/softwarecenter/ui/gtk3/session/viewmanager.py", line 148, in set_active_view
    view_widget.init_view()
  File "/usr/share/software-center/softwarecenter/ui/gtk3/panes/availablepane.py", line 152, in init_view
    self.apps_filter)
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 231, in __init__
    self.build(desktopdir)
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 516, in build
    self._build_homepage_view()
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 251, in _build_homepage_view
    self._append_new()
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 458, in _append_new
    whatsnew_cat = self._update_new_content()
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 445, in _update_new_content
    whatsnew_cat, docs = self._get_new_category_content()
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 432, in _get_new_category_content
    nonblocking_load=False)
  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 316, in set_query
    self._blocking_perform_search()
  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 211, in _blocking_perform_search
    matches = enquire.get_mset(0, self.limit, None, xfilter)
  File "/usr/share/software-center/softwarecenter/db/appfilter.py", line 74, in __call__
    if (not pkgname in self.cache and
  File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 230, in __contains__
    return self._cache.__contains__(k)
AttributeError: 'NoneType' object has no attribute '__contains__'