Making 'table' (2D built-in array) of GameObjects giving "NullReferenceException:" error

I'm making a level generator. There are two 'tables' made with 2D built-in arrays for the tiles that need to be referenced throughout gameplay: 1) Tile code (type of tile indicated by a number) 2) The actual tile GameObject (so I can delete them when necessary by referencing their position on the table)

Here is the code: using UnityEngine; using System.Collections;

 public class LevelGenerator : MonoBehaviour {
 
     // NOTES:
     // dataPos.Length is the amount of lines.
     // data actually starts on dataPos[12][0]
     // lines - 2 because there are 2 empty lines after the data
 
     // TILE CODES:
     // 0: nothing
 
     // 1: blank white tile
 
     // 2: red paint
     // 3: blue paint
     // 4: yellow paint
     // 5: purple paint
     // 6: orange paint
     // 7: green paint
 
     // 11: red empty
     // 12: blue empty
     // 13: yellow empty
     // 14: purple empty
     // 15: orange empty
     // 16: green empty
 
     // 19: 1
     // 20: 2
     // 21: 3
     // 22: 4
     // 23: 5
     // 24: 6
     // 25: 7
     // 26: 8
     // 27: 9
 
     // 28: start
     // 29: exit
 
     // 38: red door
     // 39: blue door
     // 40: yellow door
     // 41: purple door
     // 42: orange door
     // 43: green door
 
     private string[] dataLines;
     private string[][] tileTable;
     private int tileRows;
     private GameObject[][] tileObjectTable;
 
     public Cube cubeScript;
 
     public float horizontalSpace;
     public float verticalSpace;
     
     public GameObject tBlank;
     public GameObject tStart;
     public GameObject tExit;
     public GameObject tPaintRed;
     public GameObject tEmptyRed;
     public GameObject tDoorRed;
 
     public TextAsset L001;
 
     void Awake () {
         // make array with each entry being one line of the text file
         dataLines = L001.text.Split('\n');
         // make table array that has a row length equal to only the lines
         // of actual data (there are 14 lines of useless data)
         tileTable = new string[dataLines.Length - 14][];
 
 
     //    foreach (string line in dataLines) {
         for (int i = 0; i < tileTable.Length; i++) {
             // put each tile number (separated by commas) as an entry in an
             // array for each line
             tileTable[i] = dataLines[12 + i].Split (',');
         }
 
         tileObjectTable = new GameObject[tileTable.Length][];
 
         StartCoroutine ("CreateLevel");
     }
 
 
     IEnumerator CreateLevel () {
         // generate each tile
         for (int currentIncrement = 0; currentIncrement < tileTable.Length; currentIncrement++) {
             // do for each tile in the current row
             for (int i = 0; i < tileTable[currentIncrement].Length; i++) {
                 CreateTile(tileTable[currentIncrement][i], currentIncrement, i);
                 transform.position = new Vector3 (transform.position.x + horizontalSpace, transform.position.y, transform.position.z);
                 yield return new WaitForSeconds (0.05f);
                 //return null;
             }
 
             // finished that row
             currentIncrement += 1;
     
             transform.position = new Vector3 (0, transform.position.y, transform.position.z - verticalSpace);
             //yield return new WaitForSeconds (1);
             //return null;
         }
 
         // done with all the level creation, start game
         //return null;
         //Destroy (gameObject);
     }
 
     void CreateTile (string tileType, int startRow, int startColumn) {
         GameObject obj;
 
         switch (tileType) {
         case "1": 
             tileObjectTable[startRow][startColumn] = (GameObject)Instantiate(tBlank, transform.position, Quaternion.identity);
             break;
         case "2": 
             Instantiate (tPaintRed, transform.position, Quaternion.identity);
             break;
         case "11":
             Instantiate (tEmptyRed, transform.position, Quaternion.identity);
             break;
         case "28":  // start tile
             Instantiate (tStart, transform.position, Quaternion.identity);
 
             // call initialization script, giving it the entire table and the
             // player starting position on the table
             cubeScript.PlayerInitialize(tileTable, startRow, startColumn, transform.position, horizontalSpace, verticalSpace);
             break;
         case "29":
             Instantiate (tExit, transform.position, Quaternion.identity);
             break;
         case "38":
             Instantiate (tDoorRed, transform.position, Quaternion.identity);
             break;
         }
     }
 
 }

I've researched this for over 5 hours, and I've followed every 'solution' without any results. When it gets to this line on runtime: tileObjectTable[startRow][startColumn] = (GameObject)Instantiate(tBlank, transform.position, Quaternion.identity);

I get the following error: NullReferenceException: Object reference not set to an instance of an object (wrapper stelemref) object:stelemref (object,intptr,object) LevelGenerator.CreateTile (System.String tileType, Int32 startRow, Int32 startColumn) (at Assets/LevelGenerator.cs:119) LevelGenerator+c__Iterator0.MoveNext () (at Assets/LevelGenerator.cs:95)

Please help, this is driving me crazy.