personal calendar for newly created users has no calendar color set

[mbiebl]

Nextcloud: 13.0.6

When creating a new user, it by default gets a personal addressbook and calendar. Unfortunately, the calendar has not color set by default. Looking at the db dump, I see

INSERT INTO `sgnDV_calendars` (`id`, `principaluri`, `displayname`, `uri`, `synctoken`, `description`, `calendarorder`, `calendarcolor`, `timezone`, `components`, `transparent`) VALUES

(5, 'principals/users/test', 'Personal', 'personal', 1, NULL, 0, NULL, NULL, 'VEVENT,VTODO', 0);

Notice how calendarcolor is set to NULL.
Please pick a reasonable default instead of NULL

[nextcloud-bot]

GitMate.io thinks possibly related issues are #2597 (Calendar Import: "Create Calendar" option fails.), #3014 (Calendar event invitation automatically creates a new 'personal' calendar), #5040 (Upon invitations, calendar "personal" is created although there is a valid calender), #2568 (user can't change language in personal settings), and #1011 (Error while re-creating a user).

[MorrisJobke]

cc @georgehrke

[szaimen]

cc @nextcloud/calendar

[ChristophWurst]

PR is at #17148