improve async mismatch error

Author: lucasteles

src/Backdash/Session/Backends/RemoteSession.cs

@@ -615,9 +615,7 @@ void DoSync()
 
         var eps = UpdateEndpoints();
         var specs = UpdateSpectators();
-
-        if (isSynchronizing) return;
-
+        if (isSynchronizing || closed) return;
         synchronizer.CheckSimulation();
 
         // notify all of our endpoints of their local frame number for their next connection quality report
@@ -759,7 +757,10 @@ void OnNetworkEvent(in ProtocolEventInfo evt)
                 if (player.Type is PlayerType.Spectator)
                     RemoveSpectator(player);
                 else
+                {
                     Close();
+                    udp.Stop();
+                }
 
                 break;
         }
@@ -859,6 +860,9 @@ void DisconnectPlayerQueue(NetcodePlayer player, in Frame syncTo)
             $"Changing player {player} local connect status for last frame from {connStatus.LastFrame.Number} to {syncTo} on disconnect request (current: {frameCount})");
         connStatus.Disconnected = true;
         connStatus.LastFrame = syncTo;
+
+        if (closed) return;
+
         if (syncTo < frameCount && !syncTo.IsNull)
         {
             logger.Write(LogLevel.Information,

src/Backdash/Session/Backends/SpectatorSession.cs

@@ -191,9 +191,7 @@ public void BeginFrame()
         ConsumeProtocolNetworkEvents();
         host.Update();
         jobManager.ThrowIfError();
-
-        if (isSynchronizing)
-            return;
+        if (isSynchronizing || closed) return;
 
         if (lastReceivedInputTime > 0 &&
             Stopwatch.GetElapsedTime(lastReceivedInputTime) > options.Protocol.DisconnectTimeout)

src/Backdash/Synchronizing/Input/InputQueue.cs

@@ -138,7 +138,7 @@ public bool GetInput(in Frame requestedFrame, out GameInput<TInput> input)
 
             // The requested frame isn't in the queue.
             // This means we need to return a prediction frame. Predict that the user will do the same thing they did last time.
-            if (requestedFrame == 0)
+            if (requestedFrame.IsZero)
             {
                 logger.Write(LogLevel.Trace,
                     $"Queue {QueueId} => basing new prediction frame from nothing, you're client wants frame 0.");