events: handle case where organization id is null

ot_core/Classes/Domain/Repository/EventRepository.php

@@ -159,8 +159,10 @@ class EventRepository extends BaseApiRepository
         $event = new Event();
         $a = explode('/', $record['@id']);
         $event->setId(end($a));
-        $event->setOrganizationId($record['organizationId']);
-        $event->setSubdomain($record['subDomain']);
+        if ($record['organizationId'] !== null) {
+            $event->setOrganizationId($record['organizationId']);
+        }
+        $event->setSubdomain($record['subDomain'] ?? '');
         $event->setName($record['name']);
         $event->setDescription($record['description']);
         $event->setUrl($record['url']);