Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/app.py", line 525, in on_application_request_action
    self.db, self.icons):
  File "/usr/share/software-center/softwarecenter/view/dependency_dialogs.py", line 42, in confirm_install
    deps_remove = cache.try_install_and_get_all_deps_removed(appdetails.pkg)
  File "/usr/share/software-center/softwarecenter/apt/aptcache.py", line 321, in try_install_and_get_all_deps_removed
    changes = self._get_changes_without_applying(pkg)
  File "/usr/share/software-center/softwarecenter/apt/aptcache.py", line 288, in _get_changes_without_applying
    if pkg.installed == None:
AttributeError: 'NoneType' object has no attribute 'installed'