Issue Summary

When creating an event, changing the calendar while custom event selected, and creating the event without touching another thing, a default type event will be created instead of a custom one. And also, if the default types are hidden for this calendar, deleting the event is not possible without allowing the default type again.

Confluence version: 7.7.3
Team Calendars version: 6.0.53

Steps to Reproduce

screen_capture_2020_09_25.mp4

1. Create two calendars (Calendar-1, Calendar-2)
2. In the calendar edit menu, navigate to "Event Types" and hide all default event types for both calendar
3. Again in the "Event Types" menu, create one custom event type for each calendar (C1-Custom-Event for Calendar-1, C2-Custom-Event for Calendar-2)
4. Click "Add Event"
5. Leave the selected calendar on which one comes default. (ex: Calendar-1)
6. Select the custom event created for this calendar. (ex: C1-Custom-Event)
7. When the event details section is displayed, change the calendar to the other one (ex: Calendar-1 -> Calendar-2)
8. Without changing anything else, enter the event name and save it.

Expected Results

Event created with the selected custom event type.

Actual Results

Event created with the default event type.

The below exception is thrown in the Atlassian-confluence.log file:

 2020-09-25 11:08:27,188 WARN [http-nio-6773-exec-10] [extra.calendar3.util.TimeZoneUtil] tryParseDateTimeStringForEventEdit Unable to parse date null
 -- referer: http://localhost:6773/c773/calendar/mycalendar.action | url: /c773/rest/calendar-services/1.0/calendar/events.json | traceId: d57bf9ae86c3a470 | userName: admin
2020-09-25 11:08:31,098 WARN [http-nio-6773-exec-5] [confluence.impl.hibernate.ConfluenceHibernateTransactionManager] doRollback Performing rollback. Transactions:
  ->[PluginReadWriteTx]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT (Session #388162233)
 -- referer: http://localhost:6773/c773/calendar/mycalendar.action | url: /c773/rest/calendar-services/1.0/calendar/events.json | traceId: bab7e6f5ecbaae98 | userName: admin

Workaround

When creating an event, after changing the calendar with a custom event selected, even the custom event type populated correctly to the combo box, you need to choose it again. That way, you can create the event with the desired type.