Don't try to purge objects from the birthday calendar when it doesn't exist

Doesn't matter much as it's been recreated afterwards with (ensureCalendarExists).

Closes #29617

Signed-off-by: Thomas Citharel <[email protected]>

Author: tcitworld

apps/dav/lib/CalDAV/BirthdayService.php

@@ -273,6 +273,7 @@ public function buildDateFromContact(string $cardData,
 	public function resetForUser(string $user):void {
 		$principal = 'principals/users/'.$user;
 		$calendar = $this->calDavBackEnd->getCalendarByUri($principal, self::BIRTHDAY_CALENDAR_URI);
+		if (!$calendar) return; // The user's birthday calendar doesn't exist
 		$calendarObjects = $this->calDavBackEnd->getCalendarObjects($calendar['id'], CalDavBackend::CALENDAR_TYPE_CALENDAR);
 
 		foreach ($calendarObjects as $calendarObject) {