Don't show empty attributes.

Summary: Some places we pass in empty strings and get hanging middots. Would prefer not have the middot, and let the developer decide if they should set a 'nothing here' state.

Test Plan: Checked Repositories with no lint messages.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5920