Agenda: Fix when showing edit form for event without invitation - refs BT#21289

main/inc/lib/agenda.lib.php

@@ -1002,6 +1002,8 @@ class Agenda
 
                     /** @var AgendaEventSubscription $subscription */
                     $subscription = $personalEvent->getInvitation();
+
+                    if ($subscription) {
                         $subscription->setMaxAttendees($subscriptionVisibility > 0 ? $maxSubscriptions : 0);
 
                         if ($personalEvent->getSubscriptionItemId() != $subscriptionItemId) {
@@ -1013,6 +1015,7 @@ class Agenda
 
                         $em->flush();
                     }
+                }
                 break;
             case 'course':
                 $eventInfo = $this->get_event($id);
@@ -5017,7 +5020,7 @@ class Agenda
 
         if ($personalEvent) {
             $eventInvitation = $personalEvent->getInvitation();
-            $withInvitation = !($eventInvitation instanceof AgendaEventSubscription);
+            $withInvitation = $eventInvitation && !($eventInvitation instanceof AgendaEventSubscription);
 
             if ($withInvitation) {
                 foreach ($eventInvitation->getInvitees() as $invitee) {