Need Help | Door Opening Script Error

Hallo,

I'm new to unity, and this morning I tried to make a door opening by a user input. And I got an error, hope someone can help me out.

This is the error:

UnassignedReferenceException: The variable Door of 'DoorLogic' has not been assigned. You probably need to assign the Door variable of the DoorLogic script in the inspector. DoorLogic+$changeDoorState$1+$.MoveNext () (at Assets/DoorLogic.js:43) UnityEngine.MonoBehaviour:StartCoroutine_Auto(IEnumerator) DoorLogic:Update() (at Assets/DoorLogic.js:11)

Here is the code I use:

 #pragma strict
 
 var Door: Transform;
 private var drawGUI = false;
 private var doorIsClosed = true;
 
 function Update () 
 {
     if (drawGUI == true && Input.GetKeyDown(KeyCode.E))
     { 
         changeDoorState();
     }
 }
 
 function OnTriggerEnter (theCollider : Collider)
 {
     if (theCollider.tag == "Player")
     {
         drawGUI = true;
     }
 }
 
 function OnTriggerExit (theCollider : Collider)
 {
     if (theCollider.tag == "Player")
     {
         drawGUI = false;
     }
 }
 
 function OnGUI ()
 {
     if (drawGUI == true)
     {
         GUI.Box (Rect (Screen.width*0.5-51, 200, 102, 22), "Press E to open");
     }
 }
 
 function changeDoorState ()
 {
     if (doorIsClosed == true)
     {
         Door.animation.CrossFade("Open");
         //Door.audio.PlayOneShot();
         doorIsClosed = false;
         yield WaitForSeconds(3);
         Door.animation.CrossFade("Close");
         //Door.audio.Play();
         doorIsClosed = true;
     }
 }

Thanks for looking into my problem, looking forward to solve it :)