better loading indicators for timetables, talk and files

lib/api/marianumcloud/talk/room/getRoomCache.dart

@@ -7,7 +7,16 @@ import 'getRoomParams.dart';
 import 'getRoomResponse.dart';
 
 class GetRoomCache extends RequestCache<GetRoomResponse> {
-  GetRoomCache({void Function(GetRoomResponse)? onUpdate, bool? renew}) : super(RequestCache.cacheMinute, onUpdate, renew: renew) {
+  GetRoomCache({
+    void Function(GetRoomResponse)? onUpdate,
+    void Function(Exception)? onError,
+    bool? renew,
+  }) : super(
+          RequestCache.cacheMinute,
+          onUpdate,
+          onError: onError ?? RequestCache.ignore,
+          renew: renew,
+        ) {
     start('nc-rooms');
   }