[FIX] Events generates db error

As shown on the task: https://avan.tech/item78277 and on the link: https://dev.tiki.org/item8146. Calendar events were generating database errors. The first if a user does not have permission on the calendar if he tried to access it it would generate an error. Secondly if the identifier of a calendar does not exist or if the calendarid parameter is not valid.