message: fix undefined variable when enabling ascii protocol
diff: @@ -47,7 +47,6 @@ public:
  }
  } usb_packet_output;
  -#if !defined(USB_PROTOCOL_NATIVE)
  class TreatPacketSinkAsStreamSink : public StreamSink {
  public:
  TreatPacketSinkAsStreamSink(PacketSink& output) : output_(output) {}
  @@ -66,7 +65,6 @@ public:
  private:
  PacketSink& output_;
  } usb_stream_output(usb_packet_output);
  -#endif
  #if defined(USB_PROTOCOL_NATIVE)
  BidirectionalPacketBasedChannel usb_channel(usb_packet_output);
  