Public Variable Help!

In my game, I'm trying to make a wave spawner, so that when every enemy dies it will start a new wave. Right now, either the death line or the variable itself is broken. Here's my monster death system:

 var Health : float = 100;
 var MaxHealth : float = 100;
 var Manager : GameObject;
 
 function OnTriggerEnter(hit : Collider){
 if (hit.CompareTag("EditorOnly")){
 Health = Health - 1;
 }
 }
 
 function Update(){
 if (Health <= 0){
 Manager.livingCreatures = Manager.livingCreatures - 1;
 Destroy(gameObject);
 }
 }

And my Wave script (I modified it from an existing one):

     var totalCreatures : int = 2; 
     static var livingCreatures : int = 0;
     var waitToWave : float = 10;
     var waveTime : float;
     var yourCreature : Transform;
     var CurrentWave : float = 1;
     var text : GUIText;
     
     function Update() {
      text.text = CurrentWave.ToString();
         if (livingCreatures == 0) {
      
             if (waitToWave <= waveTime) {
                 waveTime = 0;
                 livesCreatures = totalCreatures;
      
                 for (var i = 0; i > totalCreatures; i++) 
                     Instantiate (yourCreature, Vector3(0,0,0), Quaternion.identity);
                     totalCreatures = totalCreatures * 2;
                      CurrentWave = CurrentWave + 1;
             }else {
                 waveTime += Time.DeltaTime;
             }
         }
     }

It's getting an error that says "NullReferenceEception: Object reference not set to an instance of an object." Please help!