public class testMovement : MonoBehaviour
{
    public GridManager GridMan;
    //List<GridTile> MovementPath = new List<GridTile>();

	void Start ()
    {
        List<GridTile> MovementPath = Astar.Pathfinding(GridMan.Grid[1][1], GridMan.Grid[3][2], GridMan);   //NullRef on this line

        Debug.Log(MovementPath.Count);

        for (int i = 0; i < MovementPath.Count; i++)
        {
            Debug.Log(MovementPath[i].GetIndex().x + " " + MovementPath[i].GetIndex().y);
        }


    }
}


NullReferenceException: Object reference not set to an instance of an object
testMovement.Start () (at Assets/Scripts/testMovement.cs:12)