message: mission: fix warning about missing return
diff: @@ -183,6 +183,8 @@ std::ostream &operator<<(std::ostream &str, MissionItem::CameraAction const &cam
  return str << "CameraAction::STOP_VIDEO";
  case MissionItem::CameraAction::NONE:
  return str << "CameraAction::NONE";
  + default:
  + return str << "Unknown";
  }
  }
  