- fix case when message of channel that isn't initialized is received

Lib.Audio/Device.cs

@@ -42,10 +42,10 @@ namespace Lib.Audio
 
         private void OnMidiCommunicationMessageReceived(object? sender, IMidiMessage message)
         {
-            IChannel channel = Channels.First(c => c.ChannelNumber == message.ChannelNumber);
+            IChannel? channel = Channels.FirstOrDefault(c => c.ChannelNumber == message.ChannelNumber);
             
-            channel.HandleMessage(message);
-            channel.SendAcknowledge();
+            channel?.HandleMessage(message);
+            channel?.SendAcknowledge();
         }
 
         private void OnMidiCommunicationErrorReceived(object? sender, IMidiMessage message) =>