Object reference not set to an instance of an object?!

HELP! I can't work out what on earth is going on here! Just so you know, I am trying to spawn two Game Objects randomly at any two of three pre-set spawn locations, while making sure that only one 'orb' appears at each.

EDIT: Perhaps I should also note that I am attaching this script to the 'spawn1' empty Game Object.

 // Currently works, however more than one GameObject often spawns at a given point.
 // FIXING
 
 var spawn : Transform[];
 var orbs : GameObject;
 var orbCount : int = 0;
 
 
 function Start () {
 
     var randomPick : int = Random.Range(1,3);
 
     if (gameObject.Find('spawn'+randomPick)) {
         Debug.Log("WORKS");
     }
 
     InvokeRepeating("spawnOrbs", 1, 1);
     
 }
 
 function Update () {
 
     if (orbCount >= 2) {
         CancelInvoke();
     }
 
 }
 
 function spawnOrbs () {
 
     var randomPick : int = Random.Range(1,2);
     
     Debug.Log(randomPick);
     
     if ("spawn"+[randomPick]) {
     
     var instance = Instantiate(orbs, gameObject.Find('spawn'+randomPick).position, transform.rotation); // Set to instance of object
     Debug.Log("Orb Spawned!");
     orbCount++;
     Destroy(gameObject.Find("spawn"+randomPick)); // Destroys spawnPoint when object spawns!
     
     } else {
     
     Debug.Log("Spawn point doesn't exist");
     
     spawnOrbs();
     
     }
 
 }

It is line "var instance = Instantiate(orbs, gameObject.Find('spawn'+randomPick).position, transform.rotation);" that throws up the error. I can't tell if it has a problem with 'orbs' or 'gameObject.Find('spawn'+randomPick)'. I should point out that I have three empty game objects named spawn1, spawn2 and spawn3 in the scene, and have dragged these into the 'spawn' variable in the inspector.