Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/view/widgets/reviews.py", line 849, in _on_realize
    self._build(review_data, app_version, logged_in_person, useful_votes)
  File "/usr/share/software-center/softwarecenter/view/widgets/reviews.py", line 972, in _build
    upstream_version_compare(review_version, app_version) != 0):
  File "/usr/share/software-center/softwarecenter/utils.py", line 219, in upstream_version_compare
    apt_pkg.upstream_version(b))
TypeError: must be string, not None