Changing variable from another script

Hello, I'm getting an error which I do not understand when trying to change a variable from a script to another script on collision. I have a score UI that always rises, and I want it to reset to 0 when it hits a certain GameObject.

The error I'm receiving is:

NullReferenceException: Object reference not set to an instance of an object CollisionDetect.OnCollisionEnter (UnityEngine.Collision theCollision) (at Assets/MyScripts/CollisionDetect.js:25)

CollisionDetect:

 function OnCollisionEnter(theCollision : Collision){
 
 if (theCollision.gameObject.name == "HighWall(Clone)")
 {
     Debug.Log("Hit the " + theCollision.gameObject.name);
     var script1: ScoreGUI = GetComponent(ScoreGUI);    
     script1.Counter=0;
 }
     
 if (theCollision.gameObject.name == "HighWall2(Clone)")
 {
     Debug.Log("Hit the " + theCollision.gameObject.name);
     var script2: ScoreGUI = GetComponent(ScoreGUI);    
     script2.Counter=0;
 }    

ScoreGUI:

 var Counter: float=1.0;
 
 function Update(){
 Counter=Counter+1.0;
 }
 
 function OnGUI(){

     GUILayout.BeginArea ( Rect ( 10, 10, Screen.width / 4, Screen.height / 4 ) );
     GUILayout.Box (Counter.ToString () );
     GUILayout.EndArea ();
     
 }

Thanks,