NullReferenceException

NullReferenceException: Object reference not set to an instance of an object
Motor.Update () (at Assets/RITD/Scripts/Motor.cs:44)

Line 44:
if (moveJoystick.InputDirection != Vector3.zero) {

using UnityEngine;
using System.Collections;

public class Motor : MonoBehaviour {
	private const float TIME_BEFORE_START = 3.0f;

	public float moveSpeed = 5.0f;
	public float drag = 0.5f;
	public float terminalRotationSpeed = 25.0f;
	public VirtualJoystick moveJoystick;

	public float boostSpeed = 5.0f;
	public float boostCooldown = 2.0f;
	private float lastBoost;

	private Rigidbody controller;
	private Transform camTransform;

	private float startTime;

	private void Start(){
		lastBoost = Time.time - boostCooldown;
		startTime = Time.time;
		controller = GetComponent<Rigidbody> ();
		controller.maxAngularVelocity = terminalRotationSpeed;
		controller.drag = drag;

		camTransform = Camera.main.transform;
	}

	private void Update(){
		if (Time.time - startTime < TIME_BEFORE_START) {
			return;
		}

		Vector3 dir = Vector3.zero;

		dir.x = Input.GetAxis ("Horizontal");
		dir.z = Input.GetAxis ("Vertical");

		if(dir.magnitude > 1)
			dir.Normalize ();

		if (moveJoystick.InputDirection != Vector3.zero) {
			dir = moveJoystick.InputDirection;
		}

		//Rotate diraction verctor with camera
		Vector3 rotatedDir = camTransform.TransformDirection(dir);
		rotatedDir = new Vector3 (rotatedDir.x, 0, rotatedDir.z);
		rotatedDir = rotatedDir.normalized * dir.magnitude;

		controller.AddForce (rotatedDir * moveSpeed);
	}

	public void Boost(){
		if (Time.time - startTime < TIME_BEFORE_START) {
			return;
		}

		if (Time.time - lastBoost > boostCooldown) {
			lastBoost = Time.time;
			controller.AddForce (controller.velocity.normalized * boostSpeed, ForceMode.VelocityChange);
		}
	}
}

A quick search about the error would tell you what it is about. You probably haven’t assigned the public variable moveJoystick from inspector. And that’s why it is null.

have u attached the Joystick ? Maybe that’s giving the error