Null Reference Exception Error in PacMan AI

Hello! I'm following a very good tutorial on how to make a pac man clone, but I stumbled upon an Null Reference Exception Error: Object reference not set to an instance of an object. You can watch the full video to see the whole code here <

>. The lines I have trouble are shown at 30.04, but here is the code:

GameObject GetPortal(Vector2 pos)
{
GameObject tile = GameObject.Find("Game").GetComponent<GameBoard>().board[(int)pos.x, (int)pos.y];
if(tile != null)
{
if (tile.GetComponent<Tile>().isPortal)
{
GameObject otherPortal = tile.GetComponent<Tile>().portalReciever;
return otherPortal;
}
}
return null;
}


The thing that is bothering me is that teh code works in every pellet, except this one.