1724 nullreferenceexception on mqttclientconnectasync (#1748)

Update MqttClient.cs

Source/MQTTnet/Client/MqttClient.cs

@@ -121,11 +121,11 @@ namespace MQTTnet.Client
                 var mqttClientAliveToken = _mqttClientAlive.Token;
 
                 var adapter = _adapterFactory.CreateClientAdapter(options, new MqttPacketInspector(_events.InspectPacketEvent, _rootLogger), _rootLogger);
-                _adapter = adapter;
+                _adapter = adapter ?? throw new InvalidOperationException("The adapter factory did not provide an adapter.");
 
                 if (cancellationToken.CanBeCanceled)
                 {
-                    connectResult = await ConnectInternal(cancellationToken).ConfigureAwait(false);
+                    connectResult = await ConnectInternal(adapter, cancellationToken).ConfigureAwait(false);
                 }
                 else
                 {
@@ -133,7 +133,7 @@ namespace MQTTnet.Client
                     // CancellationToken.None or similar.
                     using (var timeout = new CancellationTokenSource(Options.Timeout))
                     {
-                        connectResult = await ConnectInternal(timeout.Token).ConfigureAwait(false);
+                        connectResult = await ConnectInternal(adapter, timeout.Token).ConfigureAwait(false);
                     }
                 }
 
@@ -421,7 +421,7 @@ namespace MQTTnet.Client
             return CompletedTask.Instance;
         }
 
-        async Task<MqttClientConnectResult> Authenticate(MqttClientOptions options, CancellationToken cancellationToken)
+        async Task<MqttClientConnectResult> Authenticate(IMqttChannelAdapter channelAdapter, MqttClientOptions options, CancellationToken cancellationToken)
         {
             MqttClientConnectResult result;
 
@@ -435,7 +435,7 @@ namespace MQTTnet.Client
                 if (receivedPacket is MqttConnAckPacket connAckPacket)
                 {
                     var clientConnectResultFactory = new MqttClientConnectResultFactory();
-                    result = clientConnectResultFactory.Create(connAckPacket, _adapter.PacketFormatterAdapter.ProtocolVersion);
+                    result = clientConnectResultFactory.Create(connAckPacket, channelAdapter.PacketFormatterAdapter.ProtocolVersion);
                 }
                 else
                 {
@@ -484,7 +484,7 @@ namespace MQTTnet.Client
             return (MqttClientConnectionStatus)Interlocked.CompareExchange(ref _connectionStatus, (int)value, (int)comparand);
         }
 
-        async Task<MqttClientConnectResult> ConnectInternal(CancellationToken cancellationToken)
+        async Task<MqttClientConnectResult> ConnectInternal(IMqttChannelAdapter channelAdapter, CancellationToken cancellationToken)
         {
             var backgroundCancellationToken = _mqttClientAlive.Token;
 
@@ -497,7 +497,7 @@ namespace MQTTnet.Client
                 _publishPacketReceiverQueue?.Dispose();
                 _publishPacketReceiverQueue = new AsyncQueue<MqttPublishPacket>();
 
-                var connectResult = await Authenticate(Options, effectiveCancellationToken.Token).ConfigureAwait(false);
+                var connectResult = await Authenticate(channelAdapter, Options, effectiveCancellationToken.Token).ConfigureAwait(false);
 
                 _publishPacketReceiverTask = Task.Run(() => ProcessReceivedPublishPackets(backgroundCancellationToken), backgroundCancellationToken);
                 _packetReceiverTask = Task.Run(() => ReceivePacketsLoop(backgroundCancellationToken), backgroundCancellationToken);