The Commits field on the main review request box is present even if

there's no commits data to show. We end up with a label but no content.

This happens because we specify the field should be always present

unless this is on the diff viewer page (which has its own commits

representation).
We now factor in the value itself, ensuring that we only show the field

if we know we're going to end up showing a list of commits.

Tested viewing review requests with and without commits data. I could

no longer reproduce the bug where only a Commits label was shown.