[SOLVED]How to do Raycasting with Leap Motion?

I am currently try to cast the ray from the Leap Motion hand to control player's movement, and then I found this codelink text

but when I paste in my project, it keeps give me NullReferenceException

"NullReferenceException: Object reference not set to an instance of an object HandRaycast.Start () (at Assets/Script/HandRaycast.cs:25)"

Here is the code

 using Leap;
 using Leap.Unity;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class HandRaycast : MonoBehaviour {
 
     Hand leapHand;
     FingerModel finger;
     HandModel handModel;
 
     // Use this for initialization
     void Start()
     {
         /*Controller controller = new Controller();
         Frame frame = controller.Frame(); // controller is a Controller object
         if (frame.Hands.Count > 0)
         {
             List<Hand> hands = frame.Hands;
             leapHand = hands[0];
         }
         finger = leapHand.Fingers;
         Finger.FingerType fingerType = finger.Type;*/
         handModel = GetComponent<HandModel>();
         leapHand = handModel.GetLeapHand();
         if (leapHand == null) Debug.LogError("No leap_hand founded");
     }
     
     // Update is called once per frame
     void Update () {
         Vector3 fwd = transform.TransformDirection(Vector3.forward);
         RaycastHit hit;
         for (int i = 0; i < HandModel.NUM_FINGERS; i++)
         {
             finger = handModel.fingers[i];
             if (Physics.Raycast(finger.GetTipPosition(), fwd, out hit))
             {
                 float distanceToGround = hit.distance;
                 Debug.Log("hit something" + distanceToGround);
             }
             Debug.DrawRay(finger.GetTipPosition(), finger.GetRay().direction, Color.red, Time.deltaTime, true);
         }
     }
 }
 

Do any one know the solution?

Moreover, do anyone know how to scale OSVR VRFirstPersonController without canvas position affected? Everytime I adjust VRFirstPersonController scale, I do not know why the canvas on VREye1 always disappear.