Error NullReferenceException android

Unity Engine
1

Hey,
I have a script here, and when I drag it on an object called GemPrefab, it gives this error and I don’t understand what’s wrong with it.
It’s used for my adroid tablet, that when I touch it, it plays a sound, destroys the prefab and add 100 points of score.

#pragma strict
var PingGood: AudioClip; 




function Update () {

    var hit: RaycastHit;
    var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
        if (Input.touchCount > 0  Input.GetTouch(0).phase == TouchPhase.Began) 
    {
        if (Physics.Raycast (ray, hit, 100)) 
        {
            if(hit.collider.gameObject.tag == "GemPrefab")
            {
    audio.PlayOneShot(PingGood);

    Destroy (gameObject);

    ScoreBoard.SCORE = (ScoreBoard.SCORE + 100);
            }
        }
    }
}

This is the error: NullReferenceException
UnityEngine.Camera.ScreenPointToRay (Vector3 position) (at C:/BuildAgent/work/14194e8ce88cdf47/Runtime/ExportGenerated/Editor/UnityEngineCamera.cs:291)
TouchScript.Update () (at Assets/scripts/TouchScript.js:7)

I don’t understand what’s wrong. Hope for your help! Can’t get it right for weeks!

2

Looks like you destroying the wrong gameObject. You need to tell it to destroy what you touched so try Destroy (hit.gameObject); instead.

Edit: unless this script is on the gem you trying to destroy, then you might need to look at doing it a different way.

3

I still can’t find it anywhere. Can somebody just give a tutorial for android which just does this code, when the object is touched.

audio.PlayOneShot(PingGood);
Destroy (gameObject);
ScoreBoard.SCORE = (ScoreBoard.SCORE + 100);