HELP!!! This NullReferenceException won't go away! :(

Title more or less says it all. I am working on a custom board generator for a board game. Long story short I keep getting the error

NullReferenceException: Object reference not set to an instance of an object GridGenerator.GenerateGrid (UnityEngine.Texture2D t) (at Assets/Scripts/GridGenerator.cs:37) GridGenerator.Start () (at Assets/Scripts/GridGenerator.cs:24)

To be clear I have all fields filled. In fact, I checked the validity of the texture asset throughout the entire script and it always is present. However, no matter what I do, it keeps throwing this error for no reason.
Here's some of code. Pls help(...it refuses to leave. ε(´סּ︵סּ`)з ) :

 using System.Collections;
     using System.Collections.Generic;
     using UnityEngine;
     
     public class GridGenerator : MonoBehaviour
     //creates the actual grid
     {
         public Texture2D levelMap;
         //a texture from which to create the board
         public GameObject nodeGO;
         //empty gameobject to tag later
         public List<GridNode> nodes;
         //list of working nodes AKA the actual board
         void Awake()
         {
             Debug.Log(levelMap);
             //the texture exists
         
         }
         void Start() {
             Debug.Log(levelMap);
             //the texture exists
             GenerateGrid(levelMap);    
         }
     
         public void GenerateGrid(Texture2D t){
     
             Debug.Log(t);
             //the texture exists
     
             for(int x = 0; x <= t.width; x++){
                for(int y = 0; y <= t.height; y++){
                     //iterate through the grid       
                    Instantiate(nodeGO, new Vector3((float)x,0.5f,(float)y),Quaternion.identity);
                    //create the node game object for visuals
                    nodes.Add(new GridNode(new gridPos(x,y),
                             FindNeighbors(x,y,t),//<--the troublemaker?
                             false));
             }
            }
         }
     
         public gridPos[] FindNeighbors(int x, int y,Texture2D t){
             Debug.Log(t);
             //the texture exists
             gridPos[] n = new gridPos[8];
             //making sure the array doesn't exceed the maximum size for the GridNode
             int i = 0;
             //array element counter
             for (int a = x-1; a < x+1; a++){
                 for (int b = x-1; b < x+1; b++){
                     if(((!(a<0))||(!(a==x))||(!(a > t.height)))&&((!(b < 0))||(!(b==x))||!(b > t.width))){
                         //long story short check if there is a neighbor. if there is one add it to the array
                         n[i]=new gridPos(a,b);
                         Debug.Log(n[i]);
                         //the console thinks of itself to important now
                         i++;
                         //increment array element counter
                         
                     }
                     
     
                 }            
             } 
             Debug.Log(n);
             //the console is reporting a spammer
             return n;
             //return the array of neighbors
         }
        
     }


 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 //an actual grid cell
 public class GridNode{
     
     public gridPos[] neighbors {get; private set;} = new gridPos[8];
     
     public readonly gridPos Coord; 
     //it's grid position
     public bool isOccupied;
     //occupied or not?
 
     //constructor
     public GridNode(gridPos pos, gridPos[] n, bool o){
          this.Coord = pos;
          this.neighbors = n;
          this.isOccupied = o;
     }
     
 
 }
 //fancier than necessary class to pass around grid positions
 public class gridPos {
         public int x,y;
         public gridPos(int x, int y){
             this.x = x;
             this.y = y;
                     }
 }