When you delete a calendar you get a "Portlet is temporarily unavailable." message and a log stacktrace like this:
SEVERE: Servlet.service() for servlet 1 Servlet threw exception
com.liferay.calendar.NoSuchCalendarException: No Calendar exists with the primary key 21270
Steps to reproduce:
- Add a calendar portlet to a page
- Add a new calendar called "Test"
- Delete the calendar
- You get the error