Don't fatal when viewing tags pointing at commits we haven't imported/parsed yet
Summary:
In Diffusion, the "Tags" view may read commits which haven't imported or parsed yet, and thus don't have loadable objects.
Most of this logic tests for if ($commit), but the author part did not. Instead, don't render author information if $commit is not present.
Test Plan:
- Loaded tags view with commits present.
- Faked $commit = null;, loaded tag view, got this instead of a fatal:
{F5068432}
Reviewers: chad, amckinley
Reviewed By: chad
Differential Revision: https://secure.phabricator.com/D18290