message: camera: fix uninitialized memory bug
  This bug showed up very late when the bytes have been packed into a
  mavlink message and were being sent over the UDP socket.
  Tracing it back with many printfs lead me to the uninitialized variable.
diff: @@ -81,7 +81,7 @@ private:
  struct {
  std::mutex mutex {};
  - int sequence;
  + int sequence = 0; // TODO: maybe we need to start with 1, pending mavlink specs
  } _capture;
  struct {
  