Conpherence - fix a bug where users have no events

Summary: Fixes T8518. Defaulting $events to null creates carnage further down the stack. Instead, default it to array() so foreach, array_select_keys, etc. don't barf.

Test Plan: logic and will ask the reporting user to verify since they can repro 100%

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8518

Differential Revision: https://secure.phabricator.com/D13314