NullReferenceException: Object reference not set to an instance of an object

I'm sure that this has been answered somewhere else but I haven't found it yet and I sort of need to turn in this project for class tonight.

I am using Will Goldstone's "Unity Game Development Essentials" for a class and I am having a weird error creep up. (See title)

Below is my code:

     private var doorIsOpen : boolean = false;
     private var doorTimer : float = 0.0;
     private var currentDoor : GameObject;
 
     var batteryCollect : AudioClip;
     var doorOpenTime : float = 3.0;
     var doorOpenSound : AudioClip;
     var doorShutSound : AudioClip;
     
 function Update () {
 
     var hit : RaycastHit;
     
         if(Physics.Raycast (transform.position, transform.forward, hit, 5)) {
         
         if(hit.collider.gameObject.tag=="outpostDoor" && doorIsOpen == false && BatteryCollect.charge >= 4){
             GameObject.Find("Battery GUI").GetComponent(GUITexture).enabled=false;
             currentDoor = hit.collider.gameObject;
             Door(doorOpenSound, true, "dooropen", currentDoor);
                 
             }
         }
         
         else if(hit.collider.gameObject.tag=="outpostDoor" && doorIsOpen == false && BatteryCollect.charge < 4){
             GameObject.Find("Battery GUI").GetComponent(GUITexture).enabled=true;
             TextHints.message = "The door seems to need more power...";
             TextHints.textOn = true;
         }
     
     if(doorIsOpen){
         doorTimer += Time.deltaTime;
         
         if(doorTimer > 3){
             Door(doorShutSound, false, "doorshut", currentDoor);
             doorTimer = 0.0;
         }
     }
 }
 /*
 function OnControllerColliderHit(hit : ControllerColliderHit) {
     if(hit.gameObject.tag == "outpostDoor" && doorIsOpen == false){
         currentDoor = hit.gameObject;
         Door(doorOpenSound, true, "dooropen", currentDoor);
     }
 }
 */
 
 function Door(aClip : AudioClip, openCheck : boolean, animName : String, thisDoor : GameObject){
     audio.PlayOneShot(aClip);
     doorIsOpen = openCheck;
     
     thisDoor.transform.parent.animation.Play(animName);
     
 }
 
 function OnTriggerEnter(collisionInfo : Collider){
 
     if(collisionInfo.gameObject.tag == "battery"){
         BatteryCollect.charge++;
         audio.PlayOneShot(batteryCollect);
         Destroy(collisionInfo.gameObject);
     }
 }
 
 @script RequireComponent(AudioSource)

For some reason I am getting this error:

NullReferenceException: Object reference not set to an instance of an object PlayerCollisions.Update () (at Assets/Scripts/PlayerCollisions.js:24)

But I am very confused because line 24, which is:

     else if(hit.collider.gameObject.tag=="outpostDoor" && doorIsOpen == false && BatteryCollect.charge < 4){

Will not work at all if "else" is there, but once I remove it, the error continues BUT it works like its suppose to.

I'm very confused, so if anyone would be able to look at this, I would greatly appreciate it.

Thanks!