Incomplete Calibration object initialization

[andre-nguyen]

Please complete the following information:

• OS and Version: Ubuntu 18, applies to all
• ROS Version: Melodic, applies to all
• Built from Source or Downloaded from Official Repository: Source
• Version: lastest master but I think the bug was introduced in Avoid unnecessary computation #194

Describe the bug
Part of the Calibration parsing code in calibration.cc is used to retag all the laser_rings using the vertical angle. This code runs on the laser_corrections vector but not on the map, thus laser_corrections_map has incomplete initialization.

velodyne/velodyne_pointcloud/src/lib/calibration.cc

Lines 170 to 195 in 2e4e582

	double next_angle = -std::numeric_limits<double>::infinity();
	for (int ring = 0; ring < num_lasers; ++ring) {
	// find minimum remaining vertical offset correction
	double min_seen = std::numeric_limits<double>::infinity();
	int next_index = num_lasers;
	for (int j = 0; j < num_lasers; ++j) {
	double angle = calibration.laser_corrections[j].vert_correction;
	if (next_angle < angle && angle < min_seen) {
	min_seen = angle;
	next_index = j;
	}
	}
	if (next_index < num_lasers) { // anything found in this ring?
	// store this ring number with its corresponding laser number
	calibration.laser_corrections[next_index].laser_ring = ring;
	next_angle = min_seen;
	if (calibration.ros_info) {
	ROS_INFO("laser_ring[%2u] = %2u, angle = %+.6f",
	next_index, ring, next_angle);
	}
	}
	}

However, looking through the code, the map is only ever used to emit a YAML of the calibration and does it by using a forward iterator. Thus, the code below could iterate over the vector and we could technically remove that unused variable.

velodyne/velodyne_pointcloud/src/lib/calibration.cc

Lines 240 to 249 in 2e4e582

	for (std::map<int, LaserCorrection>::const_iterator
	it = calibration.laser_corrections_map.begin();
	it != calibration.laser_corrections_map.end(); it++)
	{
	out << *it;
	}
	out << YAML::EndSeq;
	out << YAML::EndMap;
	return out;
	}

To Reproduce
Read code

Expected behavior
Not have redundant datastructures.

Additional context

[JWhitleyWork]

Thanks, @andre-nguyen! Would you mind submitting a PR?