[Begginer] [Solved] How to solve a Null Reference Exception

This is the error message I am getting.. I am a beginner of coding but it was actually a tutorial on youtube I followed and I can't see what error I made even though I replayed the video many times. Thanks for any help :D

NullReferenceException: Object reference not set to an instance of an object LevelManager.PlaceTile (System.String tileType, Int32 x, Int32 y, Vector3 worldStart) (at Assets/Scripts/LevelManager.cs:60) LevelManager.Createlevel () (at Assets/Scripts/LevelManager.cs:49) LevelManager.Start () (at Assets/Scripts/LevelManager.cs:23)

This is my script

using System.Collections; using System.Collections.Generic; using UnityEngine; using System;

public class LevelManager : MonoBehaviour {

 [SerializeField]
 private GameObject[] tilePrefabs; 

 [SerializeField]
 private CameraMovement cameraMovement;
 public float TileSize

 {
     get { return tilePrefabs[0].GetComponent<SpriteRenderer> ().sprite.bounds.size.x; }
 }

 // Use this for initialization
 void Start () 
 {
     Createlevel();
 }
 
 // Update is called once per frame
 void Update ()
 {
     
 }

 private void Createlevel ()
 {
     string[] mapData = ReadLevelText ();
  

         int mapX = mapData[0].ToCharArray().Length;
         int mapY = mapData.Length;

     Vector3 maxTile = Vector3.zero;

     Vector3 worldStart = Camera.main.ScreenToWorldPoint(new Vector3 (0, Screen.height));

     for(int y = 0; y < mapY; y++) 
     {
         char[] newTiles = mapData [y].ToCharArray();
         for(int x = 0; x < mapX; x++) 
         {
             maxTile = PlaceTile (newTiles[x].ToString(),x,y,worldStart);
         }
     }

     cameraMovement.SetLimits (new Vector3(maxTile.x + TileSize, maxTile.y - TileSize));
 }

 public Vector3 PlaceTile(string tileType, int x, int y, Vector3 worldStart)
 {
     int tileIndex = int.Parse (tileType);
     TileScript newTile = Instantiate (tilePrefabs[tileIndex]).GetComponent<TileScript>();

The following line is where it says the error is

     newTile.Setup(new Point(x,y), new Vector3 (worldStart.x + (TileSize * x), worldStart.y - (TileSize * y), 0));
     return newTile.transform.position;
 }

 
 private string[] ReadLevelText()
 {
     TextAsset bindData = Resources.Load ("Level") as TextAsset;
     string data = bindData.text.Replace(Environment.NewLine,string.Empty);

     return data.Split('-');
 }

}