FPS weapon sway script error

I'm making my first FPS game and I'm using this script for weapon sway:

 var cameraObject : GameObject;
 @HideInInspector
 var targetXRotation : float;
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 var targetYRotation : float;
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 var targetXRotationV : float;
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 var targetYRotationV : float;
 
 var rotateSpeed : float = 0.3;
 
 var holdHeight : float = -0.5;
 var holdSide : float = 0.5;
 
    
 function Update () 
 {
     transform.position = cameraObject.transform.position +(Quaternion.Euler(0,targetYRotation,0) * Vector3(holdSide,holdHeight,0));
 
     targetXRotation = Mathf.SmoothDamp(targetXRotation,cameraObject.GetComponent(MouseLook).xRotation, targetXRotationV, rotateSpeed);
     targetYRotation = Mathf.SmoothDamp(targetYRotation,cameraObject.GetComponent(MouseLook).yRotation, targetYRotationV, rotateSpeed);    
     transform.rotation = Quaternion.Euler(targetXRotation, targetYRotation,0);
 }

and I get this error:

NullReferenceException: Object reference not set to an instance of an object Boo.Lang.Runtime.RuntimeServices.CheckNumericPromotion (IConvertible convertible) Boo.Lang.Runtime.RuntimeServices.CheckNumericPromotion (System.Object value) Boo.Lang.Runtime.RuntimeServices.UnboxSingle (System.Object value) GunScriptE.Update () (at Assets/Scripts/GunScriptE.js:21)

My gun behaviour is very strange now. How can I fix this because no matter what I try, it won't work! I'm new here so I apologize that! Thanks