I'm having problems instaniating

I'm trying to be able to click a button and rotation around an object and then continue moving in a new direction based off of the rotation of the ship.

So the ship is a triangle, and the front is where the smallest angle is (like a ship). I have a cube that I'm able to rotate around and the radius is not fixed, the radius is however distant I am from the cube when I press a button. When I rotate the "front" of the ship will change or also the 'y rotation' I then want to continue moving in the direction that the 'y rotation' is facing if that makes any sense.

So all that is working, but now I'm working on being able to have multiple points on the screen that I can rotate around. I also want to be able to rotate the correct way that I'm facing ( the current situation is that I can only rotate clockwise.

I'm having problems getting to that point, I'm trying to instantiate an empty game object to get some reference to adjust rotation and set up so I can have multiple points to use. This is the error I'm getting

 NullReferenceException: Object reference not set to an instance of an object
 NewControll.Update () (at Assets/Scripts/NewControll.cs:49)

Here is the code. C#

 using UnityEngine;
 using System.Collections;
 
 public class NewControll : MonoBehaviour {
     
     GameObject cube;
     public GameObject Player;
     public Transform center;
     public Vector3 axis = Vector3.up;
     public Vector3 desiredPosition;
     public float radius;
     public float radiusSpeed;
     public float rotationSpeed;
 
 
     public float speed;
     public float tilt;
     public Boundary boundary;
     
     public GameObject shot;
     public Transform shotSpawn;
     public float fireRate;
     
     private float nextFire;
 
     private Transform refpoint;
     public Transform ballsack;
 
     
     void Start () {
         cube = GameObject.FindWithTag("Cube");
         center = cube.transform;
         refpoint = cube.transform;
         transform.position = (transform.position - center.position).normalized;
 
     }
         
     void Update () 
     {
         if (Input.GetButton("Fire1")) 
         {
             Vector3 zerovec = new Vector3(0,0,0);
             GetComponent<Rigidbody>().velocity = zerovec;
             transform.RotateAround (center.position, axis, rotationSpeed * Time.deltaTime);
             GameObject biscut;
             biscut = Instantiate(ballsack, refpoint.position, refpoint.rotation)as GameObject;
             biscut.transform.parent = gameObject.transform;
             Debug.Log(biscut.transform.localPosition);
 
             Destroy(biscut);
 
             //desiredPosition = (transform.position - center.position).normalized * radius + center.position;
             //transform.position = Vector3.MoveTowards (transform.position, desiredPosition, Time.deltaTime * radiusSpeed);
         }
         else
         {
             GetComponent<Rigidbody>().velocity = Player.transform.rotation * Vector3.forward * speed;
 
         }
     }
 }