catch cancled task exception in notif

BTCPayServer/Controllers/NotificationsController.cs

@@ -78,19 +78,23 @@ namespace BTCPayServer.Controllers
             IEventAggregatorSubscription subscription = null;
             try
             {
-                subscription =  _eventAggregator.Subscribe<UserNotificationsUpdatedEvent>(async evt =>
+                subscription = _eventAggregator.Subscribe<UserNotificationsUpdatedEvent>(async evt =>
                 {
                     if (evt.UserId == userId)
                     {
                         await websocketHelper.Send("update");
                     }
                 });
-               
+
                 while (!cancellationToken.IsCancellationRequested)
                 {
                     await Task.Delay(2000, cancellationToken);
                 }
             }
+            catch(TaskCanceledException)
+            {
+                // ignored
+            }
             finally
             {
                 subscription?.Dispose();