Previously, when an unauthenticated user attempted to view the 'All

Review Requests' page, every summary would be None. This was because

the SummaryColumn would attempt to evalute the

review_request.visibility attribute, but it is only defined when the

user is authenticated. This would lead to an exception being raised in

the rendering and None being returned instead. This patch fixes the

issue by only attempting to render the review request visibility when

the user viewing the datagrid is authenticated.

The archived and muted state is correctly shown.
The summaries are correctly rendered in the datagrid.