Conpherence - fix widget updates from main view

Summary: Fixes T8217. Broken circa D12760. Some browsers rendered nothing while others rendered a ",".

Test Plan: added folks to conpherences and saw people widget update correctly. added files to conpherence and saw file widget update correctly. Tested on Chrome and Firefox.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8217

Differential Revision: https://secure.phabricator.com/D12912