fix spectator remote player query

Author: lucasteles

src/Backdash/Session/Backends/LocalSession.cs

@@ -55,7 +55,7 @@ SessionServices<TInput> services
         this.options = options;
     }
 
-    public void Dispose() => tsc.SetCanceled();
+    public void Dispose() => tsc.TrySetCanceled();
 
     public async ValueTask DisposeAsync() => await WaitUntilFinish();
 

src/Backdash/Session/Backends/SpectatorSession.cs

@@ -388,4 +388,10 @@ bool IProtocolInputEventPublisher<ConfirmedInputs<TInput>>.Publish(in GameInputE
         host.SetLocalFrameNumber(input.Frame, FixedFrameRate);
         return host.SendInputAck();
     }
+
+    bool INetcodeSession.TryGetRemotePlayer([NotNullWhen(true)] out NetcodePlayer? player)
+    {
+        player = host.Player;
+        return true;
+    }
 }