Remove extra space under PHUIActionPanel

Summary: If we don't have a state in PHUIActionPanelView, don't set the extra padding to display it.

Test Plan: Review in UIExamples.

Reviewers: epriestley, btrahan

Reviewed By: btrahan

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11814