Help with JS script

I recently got some help with this script but now it is playing up again so i am back for more help It is giving me the error

 NullReferenceException: Object reference not set to an instance of an object
 Coin.OnTriggerEnter2D (UnityEngine.Collider2D other) (at Assets/Coin.js:11)

which means it is not being called or something like that but i dont know why here is the two scripts

Coin script:

 #pragma strict
 
 var Money : MenuShopSystem ;
 functi

on Start () {

}

function OnTriggerEnter2D (other: Collider2D) { Debug.Log ("Touch"); Money.Money += 100; Destroy(gameObject.Find("Coin"));

}

Shop script (what the coin script is calling from)

     #pragma strict
     //add this script to any gameObject you want//
     
     
     
     //paste this to add more items to youre shop:
     // if(GUI.Button(Rect(Screen.width/2,Screen.height/2,150,150), Item)){
     // if(Money >= 200){
     // Money -= 200;
     // }else{
     // Money -=0;
     // }
     // }
     // GUI.Button(Rect(Screen.width/2+150,Screen.height/2,150,150), "Buy: 200");
     
     
     
     //variables----------------------------------------
     var ShowShop = false;
     var CoinTexture : Texture;
      public var Money :int=0;
     var skin : GUISkin;
     var AddButton = false;
     //Items:
     //to add more items just copy this variable and add the item name;
     
     var Item : Texture;
     var Item2 :Texture;
     var Item3 :Texture;
     
     //code----------------------------------------
     function Start () {
     Money = PlayerPrefs.GetInt("Money", 0);
     }
     function Update () {
     PlayerPrefs.SetInt ("Money", Money);
     if(Money <= 0){
     Money = 0;
     }
     }
     
     
     function OnGUI(){
     GUI.skin = skin;
     if(ShowShop ==true){
     //money{********************-------------------------------------------------------------**************************
     GUI.Button(Rect(Screen.width/60,Screen.height/60  ,50,50), CoinTexture);
     GUI.Button(Rect(Screen.width/60+50,Screen.height/60  ,70,50), ""+Money);
     if(AddButton ==true){
     if(GUI.Button(Rect(Screen.width/60+120,Screen.height/60  ,70,50), "Add")){
     Money += 100;
     }
     }
     //money}***********************-------------------------------------------------------------------*****************************
     
     //Items(Shop){
     if(GUI.Button(Rect(Screen.width/2,Screen.height/2,150,150), Item)){
     if(Money >= 200){
     Money -= 200;
     }else{
     Money -=0;
     }
     }
     GUI.Button(Rect(Screen.width/2+150,Screen.height/2,150,150), "Buy: 200");
     
     if(GUI.Button(Rect(Screen.width/2,Screen.height/2- -150,150,150), Item2)){
     if(Money >= 150){
     Money -= 150;
 
 }else{
 Money -=0;
 }
 }
 GUI.Button(Rect(Screen.width/2+150,Screen.height/2- -150,150,150), "Buy: 150");
 
 if(GUI.Button(Rect(Screen.width/2,Screen.height/2- 150,150,150), Item3)){
 if(Money >= 500){
 Money -= 500;
 }else{
 Money -=0;
 }
 }
 GUI.Button(Rect(Screen.width/2+150,Screen.height/2- 150,150,150), "Buy: 500");
 //Items(Shop)}
 
 
 }
 }//OnGUI End////////////////////////////////////