Don't render an action list without actions

Summary: Skips rendering of partial elements if no actions are present.

Test Plan: Tested on profile menu item page, maniphest curtain, phriction dropdown, and instance backups page (no actions at all).

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D17931