R1:604b78095349

Fix an issue where 'Attending' would appear on calendar view unnecessarily

Summary:
Ref T10295

* Viewing Upcoming Events in the calendar would display 'Attending: ' even if there were not attendees. This caused confusion, such as 'Is it telling me I am "Attending?"'
* When a calendar event has no attendees, simply do not display the 'Attending: ' label

Test Plan:
* Add a new event with no one attending.
* Add a new event with one or more attendees.
* View the Upcoming Events query of the Calendar app.
*…