Fix a null ref exception.

At that time the remote even doesn't exist.
Also this debug output doesn't make any sense because when handling
udp request, this tcp connection won't have any meaningful data.
So I simply removed these two lines.

Signed-off-by: noisyfox <timemanager.rick@gmail.com>

shadowsocks-csharp/Controller/Service/TCPRelay.cs

@@ -303,7 +303,6 @@ namespace Shadowsocks.Controller
                 if (ar.AsyncState != null)
                 {
                     connection.EndSend(ar);
-                    Logging.Debug(remote.LocalEndPoint, remote.DestEndPoint, RecvSize, "TCP Relay");
                     connection.BeginReceive(_connetionRecvBuffer, 0, RecvSize, SocketFlags.None, new AsyncCallback(ReadAll), null);
                 }
                 else
@@ -311,7 +310,6 @@ namespace Shadowsocks.Controller
                     int bytesRead = connection.EndReceive(ar);
                     if (bytesRead > 0)
                     {
-                        Logging.Debug(remote.LocalEndPoint, remote.DestEndPoint, RecvSize, "TCP Relay");
                         connection.BeginReceive(_connetionRecvBuffer, 0, RecvSize, SocketFlags.None, new AsyncCallback(ReadAll), null);
                     }
                     else