Fix error when collection is null in collection notification (#38831)

app/javascript/mastodon/features/notifications_v2/components/notification_collection.tsx

@@ -24,9 +24,14 @@ export const NotificationCollection: React.FC<{
   unread: boolean;
 }> = ({ notification, unread }) => {
   const { collection, type } = notification;
-  const collectionCreatorAccount = useAccount(collection.account_id);
+
+  const collectionCreatorAccount = useAccount(collection?.account_id);
   const confirmRevoke = useConfirmRevoke(collection);
 
+  if (!collection) {
+    return null;
+  }
+
   return (
     <div
       className={classNames(