Refactoring CalendarEventSearchEngine to fit new null handling of AphrontFormDateControlValue
Summary: Ref T4393, Refactoring CalendarEventSearchEngine to fit new null handling of AphrontFormDateControlValue
Test Plan: Use calendar query for day view, expect no php errors
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin, epriestley
Maniphest Tasks: T4393
Differential Revision: https://secure.phabricator.com/D12701