Unity crashes when trying to make marching terrain

Hello i am trying to make terrain that marches when player moves but for now i am trying to just build 3 x 3 terrain around player

this is code i wrote:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Marching : MonoBehaviour
6. {
7.     public Transform Player;
8.  
9.     Transform[] ChunkCopy;
10.     Transform Chunk;
11.  
12.     Vector3[] ChunkPositions;
13.  
14.     int PositionOffset = 100;
15.  
16.     int ChunkX;
17.     int ChunkY;
18.  
19.     void Start()
20.     {
21.         Generate();
22.     }
23.  
24.     void Generate ()
25.     {
26.         ChunkX = 3;
27.         ChunkY = 3;
28.  
29.         Chunk = this.gameObject.transform;
30.  
31.         ChunkPositions = new Vector3[ChunkX * ChunkY];
32.         ChunkCopy = new Transform[ChunkX * ChunkY];
33.  
34.         for (int ChunkIndexZ = 0, ChunkIndexX = 0, index = 0, x = 0;x< ChunkX;x++)
35.         {
36.             for (int y = 0;y< ChunkY; y++)
37.             {
38.                 ChunkPositions[index] = new Vector3(Player.position.x - PositionOffset, 0, Player.position.z - PositionOffset);
39.  
40.                 index++;
41.                 ChunkIndexX += 10;
42.             }
43.             ChunkIndexZ += 10;
44.         }
45.  
46.         for (int Index = 0, x = 0; x <= ChunkX; x++)
47.         {
48.             for (int y = 0; y <= ChunkY; y++)
49.             {
50.                 ChunkCopy[Index] = Instantiate(Chunk, ChunkPositions[Index], Quaternion.identity);
51.             }
52.         }
53.     }  
54. }
55.  

i am not sure what is wrong with it. when i try to play unity crashes