how to disable patent components incode

I'm trying to make a turret where the player can get in and out of the turret. but activating/deactivating the turrets script does not work, the script is on the fps controller and the turret script is on the parent, how can I do this?

 #pragma strict
 
 function Start () {
 
 }
 var inturret : boolean;
 function Update () {
 //debug ray cast down
  var fwd = transform.TransformDirection(Vector3.forward);
  
  var hit : RaycastHit;
  
  var ray = new Ray (transform.position, transform.forward);
  
  var forward : Vector3 = transform.TransformDirection(Vector3.forward) * 2;
  
     Debug.DrawRay (transform.position, forward, Color.green);
 //end of debug raycast  
 
 if (Input.GetKeyDown(KeyCode.F)){
 
 if (inturret == false){
 //making raycast
  var fwd2 = transform.TransformDirection(Vector3.forward);
  
  var hit2 : RaycastHit;
  
  var ray2 = new Ray (transform.position, transform.forward);
  
 if (Physics.Raycast (ray2, hit2, 2)){
 
 Debug.Log(hit2.distance);
 //it is detecting the tag
  if (hit2.collider.CompareTag("Eturret")){
  
   Debug.Log("test");
   //making the turret a variable 
   var turret = hit2.transform;
   
 //  turret.parent = transform;
 //making the transforms parent the turret
   transform.parent = turret;
   //setting the inturret boolean to true
   inturret = true;
   
   
 //var script : ScriptName = transform.parent.GetComponet(turretfire);
 
     //var script : Transform;
     
     //script = transform.parent;
     
  // script.GetComponent(turretfire).enabled = true;
  
  //this is the line of code that is trying to activate the turret fire script
   transform.parent.GetComponent(turretfire).enabled = true;
   
  }
 } 
 
 } else {
 
 transform.parent = null;
 
 inturret = false;
 
 }
 
 }
 
 }
 //GetComponent(MyScript).enabled = false;
 //camera.enabled = false;

the error I am getting is NullReferebceExeption: Object reference not set to an instance of an object

this is for the transform.parent.GetComponent line