Object Does not Destroyed While Shooting

I am currently Learning Unity. I have created First person Controller with gun under the main camera in hierarchy.but when i shoot an object i get runtime error :

 nullreference exception : object reference not set to an instance of an object.

I have written code for shooting :

Here is my code:

 var shotSound: AudioClip; // drag a shot sound here, if any
 
 // the PickupController component of the 'PickupSpawnPoints' GameObject
 private var pickupController:PickupController;
 
 function Update(){
   if (Input.GetKey(KeyCode.Space)) {
 
       Shoot();
       }
 } 
 
 function Shoot(){
     if (shotSound) audio.PlayOneShot(shotSound); // play the shot sound
        var hit: RaycastHit;
     var ray : Ray = Camera.main.ViewportPointToRay (Vector3(0.5,0.5,0));
      
     if (Physics.Raycast (ray ,hit))
     {
         var pickupSpawnPoints:GameObject = hit.collider.gameObject;
         if(pickupSpawnPoints.tag == "Pickup")
         {
             pickupSpawnPoints.GetComponent(typeof(PickupController)).Collected(pickupSpawnPoints); // here i get error.
         }
     }       
 }

Calling function is here:

 function Collected(pickupCollected:GameObject)
 {
     // retrieve name of the collected pickup and cast to int
     var index:int = parseInt(pickupCollected.name);
      
     // pickup has been destroyed so make the spawn index available again
     spawnIndexAvailableList[index] = true;
      
     // retrieve the pickup state
     var type:int = pickupCollected.GetComponent(Pickup).type;
      
     // update the score depending on the type of pickup
     if (type == 1) 
     {
         score+=2; // simply add 2 to the score
     }
     else if (type == 2)
     {
         score += Random.Range(-2, 5); // add a random score between -2 and 5 to the score
     }
      
     // update the score
     UpdateScoreText();
      
     // destroy the pickup
     Destroy(pickupCollected);
      
     // wait for a random amount of seconds between minimumSpawnDelayTime and maximumSpawnDelayTime
     yield WaitForSeconds(Random.Range(minimumSpawnDelayTime, maximumSpawnDelayTime));
      
     // spawn a new pickup
     SpawnPickup();
 }

So how do i destroy my object.? how do i solve my error? I have no idea about it so please help me. Thanks in Advance for your support.