Having trouble getting past NullReferenceException

Having trouble getting past NullReferenceException

I'm a newbie in programming, especially in c#. I have written some code
but I keep getting an error when running it and I can't move on until I
get that fixed.
The error in question is a NullReferenceException. It also tells me
"Object reference not set to an instance of an object".
It seems like a pretty clear error message indicating that an object
hasn't been instantiated yet. However I thought I had done that. I hope
someone can explain to me what I'm doing wrong. Here's my code.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace EvenHelemaalOvernieuw
{
class Globals
{
public static int size = 50;
public static int factor = 3;
public static int puzzleNumber = 1;
public static Square[,] allSquares = new Square[Globals.factor *
Globals.factor, Globals.factor * Globals.factor];
public static String path = @"" + factor.ToString() + "\\" +
puzzleNumber.ToString() + ".txt";
public static int[,][,] values = new int[factor, factor][,];
public Globals()
{
}
public void setSize(int s)
{
size = s;
if (size > 100)
{
size = 100;
}
if (size < 20)
{
size = 20;
}
}
public void setFactor(int f)
{
factor = f;
if (factor > 5)
{
factor = 5;
}
if (factor < 2)
{
factor = 2;
}
}
public Square getSquare(int x, int y)
{
return allSquares[x, y];
}
public static void readPuzzle()
{
List<int> conversion = new List<int>();
int count = 0;
using (StreamReader codeString = new StreamReader(path))
{
String line = codeString.ReadToEnd();
Array characters = line.ToCharArray();
foreach (char a in characters)
{
if (a.ToString() != ",")
{
conversion.Add(Convert.ToInt32(a));
}
}
for (int panelX = 0; panelX < factor; panelX++)
{
for (int panelY = 0; panelY < factor; panelY++)
{
for (int squareX = 0; squareX < factor; squareX++)
{
for (int squareY = 0; squareY < factor; squareY++)
{
values[panelX, panelY][squareX, squareY] =
conversion[count];
count++;
}
}
}
}
}
}
}
}
The line that is indicated by the error message is near the bottom and
reads "values[panelX, panelY][squareX, squareY] = conversion[count];".