Unity NullReferenceException: Object reference not set to an instance of an object на 31 строчке

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class player : MonoBehaviour
{
    public ControlType controlType;
    public Joystick joystick;
    public float speed;

    public enum ControlType{PC, Android}

   
    private Rigidbody2D rd;
    private Vector2 moveInput;
    private Vector2 moveVelocity;
    void Start()
    {
        rd = GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void Update()
    {
        if (controlType == ControlType.PC)
        {
            moveInput = new Vector2(Input.GetAxisRaw("Horizontal"), Input.GetAxisRaw("Vertical"));
        }
        else if(controlType == ControlType.Android)
        {
            moveInput = new Vector2(joystick.Horizontal, joystick.Vertical);
        }
        moveVelocity = moveInput.normalized * speed;
    }

    void FixedUpdate()
    {
        rd.MovePosition(rd.position + moveVelocity * Time.fixedDeltaTime);
    }
}