Fix issues with collided vehicle not being detected

[emocat]

When on_collision is set on the ego vehicle and it collides with a npc, we notice that Python API returns NULL through the ws socket with lgsvl:

{"result":{"events":[{"type":"collision","agent":"eb657a86-0d2a-4bd5-9d91-184469100ee7","other":null,"contact":{"x":107.696556091309,"y":0.237456381320953,"z":32.5612945556641}}]}}

Obviously that other object in AddCollision() is not corresponded with added agent objects before:

simulator/Assets/Scripts/Api/ApiManager.cs

Lines 350 to 370 in 26b53c1

	public void AddCollision(GameObject obj, GameObject other, Collision collision = null)
	{
	if (!Collisions.Contains(obj) || (collision != null && collision.gameObject.layer == roadLayer))
	{
	return;
	}
	string uid1, uid2;
	if (AgentUID.TryGetValue(obj, out uid1))
	{
	var j = new JSONObject();
	j.Add("type", new JSONString("collision"));
	j.Add("agent", new JSONString(uid1));
	if (AgentUID.TryGetValue(other, out uid2))
	{
	j.Add("other", new JSONString(uid2));
	}
	else
	{
	j.Add("other", JSONNull.CreateOrGet());
	}

We notice implementation of OnTriggerEnter in VehicleController.cs is a bit different from that in NPCController.cs. After modifying collision.gameObject to collision.attachedRigidbody.gameObject, the collided vehicles can be successfully resolved.

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[xli149]

Hi emocat,

I've made the change as you suggested and run random-traffic-local through the Python API. However, the return value is still None for collision npcs. Could you give any suggestions?
@emocat
Best,
Chris