Handle "free/busy" Calendars

[lbell]

Possible that calendars set the show only free/busy result in "undefined" title. If that's the case, should see if we can tap in to show "busy" or custom message.

[adster101]

This is an issue for us. See the calendar here for example - https://jimralleyaa701a90f1.wpcomstaging.com/whats-on/

Can you point me in the right direction and I'll see if I can come up with a fix? Seems like it shouldn't be that difficult ;-)

[lbell]

This is a longstanding issue with FullCalendar: fullcalendar/fullcalendar#6617

Possibly, we could modify the event object with the setProp to find undefined titles and replace them. Haven't dug deep enough to know if this is the right route.