Correct ObjectItem height when no attributes are attached

Summary: If we have a byline, but no attributes, the height of the entire object is off by 4 pixels.

Test Plan: Review list of recent commits, see correct padding.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11128