message: mission: fix double promotion error
diff: @@ -544,7 +544,7 @@ void MissionImpl::assemble_mission_items()
  } else if (it->command == MAV_CMD_IMAGE_START_CAPTURE) {
  if (it->param2 > 0 && int(it->param3) == 0) {
  new_mission_item->set_camera_action(MissionItem::CameraAction::START_PHOTO_INTERVAL);
  - new_mission_item->set_camera_photo_interval(it->param2);
  + new_mission_item->set_camera_photo_interval(double(it->param2));
  } else if (int(it->param2) == 0 && int(it->param3) == 1) {
  new_mission_item->set_camera_action(MissionItem::CameraAction::TAKE_PHOTO);
  } else {
  