Restrict Differential buckets to just ApplicationSearch views
Summary: Ref T9363, If we're in a dashboard panel, only show buckets with data, or a fallback if nothing exists.
Test Plan: Test 'active revisions' panel in a dashboard and in Differential.
Reviewed By: epriestley
Maniphest Tasks: T9363
Differential Revision: https://secure.phabricator.com/D17544