Fix calendar events with empty "eventtype" field during upgrade.

• This needs to be tested on all supported databases
• This needs to be tested on all patched branches
• The testing needs, changes both before and after the patch is applied.

Testing instructions

1. Create calender event of type user, group, site, due(Assignment) on a site without the patch
   • site events (sitepages->calendar->new event->type>site)
   • user events (sitepages->calendar->new event->type->user)
   • group events(sitepages->calendar->new event->type->group) (you must have multiple groups)
   • due events (Create an assign module with a future due date)
   • due events (Create an assignment module with a future due date)
2. Goto database and make a note of id and their associated "Eventtype" in the table "Event"
3. Delete the values in the column 'eventtype'
4. Apply the patch
5. it should prompt you for an upgrade, run the upgrade.
6. Goto database again and make sure all events have "Eventtype" as noted on step 2
7. visit the calendar and make sure no errors are shown
8. Repeat with atleast one more database
   TEST 2
9. Backup a course with calendar event
10. check the box "include calendar events" while backing up
11. open the backup file and edit the calendar.xml to remove event type
12. restore the new backup file
13. make sure the new course has calendar events with appropriate event types