fix(caldav): Throw 403 Forbidden Error instead of 500 Internal Server…

… Error

Signed-off-by: SebastianKrupinski <krupinskis05@gmail.com>

apps/dav/lib/CalDAV/CalDavBackend.php

@@ -65,6 +65,7 @@
 use Sabre\VObject\Property;
 use Sabre\VObject\Reader;
 use Sabre\VObject\Recur\EventIterator;
+use Sabre\VObject\Recur\NoInstancesException;
 use function array_column;
 use function array_map;
 use function array_merge;
@@ -2987,7 +2988,15 @@ public function getDenormalizedData(string $calendarData): array {
 					$lastOccurrence = $firstOccurrence;
 				}
 			} else {
-				$it = new EventIterator($vEvents);
+				try {
+					$it = new EventIterator($vEvents);
+				} catch (NoInstancesException $e) {
+					$this->logger->debug('Caught no instance exception for calendar data. This usually indicates invalid calendar data.', [
+						'app' => 'dav',
+						'exception' => $e,
+					]);
+					throw new Forbidden($e->getMessage());
+				}
 				$maxDate = new DateTime(self::MAX_DATE);
 				$firstOccurrence = $it->getDtStart()->getTimestamp();
 				if ($it->isInfinite()) {