GoogleMapTile.csのエラー

Question

###使用してる参考書
UnityによるARゲーム開発

###質問内容
tileの上にGoogle static mapから地図を持ってきて貼ろうとしているのですが，配布されるGoogleMapTile.csにおいてエラーが出てしまいました．
一旦この部分は問題なく通っていたのですが，本日projectを開いてみたところ，objectがmissingとなっているものがあり，その修正をしていたら，今までに出ていないエラーが出てしまったという流れです．

errorになってる関数が調べても出てこなくてどうすればいいのかわからなくなっています．

APIキーを貼らないと表示されないという問題はすでに解決済みです．

###エラー内容
NullReferenceException: Object reference not set to an instance of an object
packt.FoodyGO.Mapping.GoogleMapTile+<_RefreshMapTile>d__16.MoveNext () (at Assets/FoodyGo/Scripts/Mapping/GoogleMapTile.cs:132)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <d29d557b212f474390dc0b17ef6ce0dd>:0)

###問題となっている文

gpsLocationService.MapRedrawn();

###コード全体(APIキーは隠してあります)

using UnityEngine;
using UnityEngine.Networking;
using System.Collections;
using packt.FoodyGO.Services;

namespace packt.FoodyGO.Mapping
{
    [AddComponentMenu("Mapping/GoogleMapTile")]
    public class GoogleMapTile : MonoBehaviour
	{
		public enum MapType
		{
			RoadMap,
			Satellite,
			Terrain,
			Hybrid
		}

		//Google Maps API Staticmap URL
		private const string GOOGLE_MAPS_URL = "https://maps.googleapis.com/maps/api/staticmap";

		[Header("Map Settings")]
		[Range(1,20)]
		[Tooltip("Zoom Level, 1=global - 20=house")]
		public int zoomLevel = 1;
		[Tooltip("Type of map, Road, Satellite, Terrain or Hybrid")]
		public MapType mapType = MapType.RoadMap;
		[Range(64,1024)]
		[Tooltip("Size in pixels of the map image")]
		public int size = 640;
		[Tooltip("Double the pixel resolution of the image returned")]
		public bool doubleResolution = true;
		[Tooltip("Defines the origin of the map")]
		public MapLocation worldCenterLocation;

		[Header("Tile Settings")]
		[Tooltip("Sets the tiles position in tile units")]        
        public Vector2 TileOffset;
		[Tooltip("Calculated tile center")]
		public MapLocation tileCenterLocation;
		[Tooltip("Calculated tile corners")]
        public Vector2 TopLeftCorner;
        public Vector2 BottomRightCorner;

		[Header("GPS Settings")]
		[Tooltip("GPS service used to locate world center")]
		public GPSLocationService gpsLocationService;
        private double lastGPSUpdate;

		// Use this for initialization
		void Start ()
		{
			RefreshMapTile ();
		}
	
		// Update is called once per frame
		void Update ()
		{
			//check if a new location has been acquired
            if (gpsLocationService != null &&
                gpsLocationService.IsServiceStarted && 
                lastGPSUpdate < gpsLocationService.Timestamp)
            {
                lastGPSUpdate = gpsLocationService.Timestamp;
                worldCenterLocation.Latitude = gpsLocationService.Latitude;
                worldCenterLocation.Longitude = gpsLocationService.Longitude;
                print("GoogleMapTile refreshing map texture");
                RefreshMapTile();
            }
		}

		public void RefreshMapTile() {
			
			StartCoroutine(_RefreshMapTile());
		}

		IEnumerator _RefreshMapTile ()
		{            
			//find the center lat/long of the tile
			tileCenterLocation.Latitude = GoogleMapUtils.adjustLatByPixels(worldCenterLocation.Latitude, (int)(size * 1 * TileOffset.y), zoomLevel);
			tileCenterLocation.Longitude = GoogleMapUtils.adjustLonByPixels(worldCenterLocation.Longitude, (int)(size * 1 * TileOffset.x), zoomLevel);

			var queryString = "";

			//build the query string parameters for the map tile request
			queryString += "center=" + WWW.UnEscapeURL (string.Format ("{0},{1}", tileCenterLocation.Latitude, tileCenterLocation.Longitude));
			queryString += "&zoom=" + zoomLevel.ToString ();
			queryString += "&size=" + WWW.UnEscapeURL (string.Format ("{0}x{0}", size));
			queryString += "&scale=" + (doubleResolution ? "2" : "1");
			queryString += "&maptype=" + mapType.ToString ().ToLower ();
			queryString += "&format=" + "png";

            //adding the map styles
            queryString += "&style=element:geometry|invert_lightness:true|weight:3.1|hue:0x00ffd5";
            queryString += "&style=element:labels|visibility:off";

            //queryString += "&key={your API key here}";

            //check if script is on a mobile device and using a location service s
            var usingSensor = false;
#if MOBILE_INPUT
            usingSensor = Input.location.isEnabledByUser 
							&& Input.location.status == LocationServiceStatus.Running 
							&& gpsLocationService !=null;
#endif
			queryString += "&sensor=" + (usingSensor ? "true" : "false");

			//set map bounds rect
			TopLeftCorner.x = GoogleMapUtils.adjustLonByPixels(tileCenterLocation.Longitude, -size, zoomLevel);
			TopLeftCorner.y = GoogleMapUtils.adjustLatByPixels(tileCenterLocation.Latitude, size, zoomLevel);

			BottomRightCorner.x = GoogleMapUtils.adjustLonByPixels(tileCenterLocation.Longitude, size, zoomLevel);
			BottomRightCorner.y = GoogleMapUtils.adjustLatByPixels(tileCenterLocation.Latitude, -size, zoomLevel);

            print(string.Format("Tile {0}x{1} requested with {2}", TileOffset.x, TileOffset.y, queryString));

			//finally, we request the image
            var req = UnityWebRequestTexture.GetTexture(GOOGLE_MAPS_URL + "?" + queryString + "&key");
			//yield until the service responds
            yield return req.Send();
			//first destroy the old texture first
			Destroy(GetComponent<Renderer>().material.mainTexture);
			//when the image returns set it as the tile texture
            if (req.error != null) {
                print (string.Format ("Error loading tile {0}x{1}:  exception={2}",
                    TileOffset.x, TileOffset.y, req.error));
            } else {
                //when the image returns set it as the tile texture
                GetComponent<Renderer> ().material.mainTexture = ((DownloadHandlerTexture)req.downloadHandler).texture;
                print (string.Format ("Tile {0}x{1} textured", TileOffset.x, TileOffset.y));
                if (TileOffset.x == 0 && TileOffset.y == 0) {
                    gpsLocationService.MapRedrawn();
                }
            }
        }
	}
}

Answer 1

TileにGPSを付けていないのが原因でした