Object reference not set to an instance of an object

I have two scripts.

The 'Health' script component, placed on the 'Player' reloads the scene if the health drops below 0.

  public var startHealth : float = 10f;
     public var health : float = 10f;
     public var sceneToLoad : String = "Test";
     
     function Start()
         {
         health = startHealth;
         }
     
     function Update()
         {
         if (health <= 0f )
             LevelReset();
         }
     
     function LevelReset()
         {
         Application.LoadLevel (sceneToLoad);
         }

And the 'CollisionDamage' script, attached to the 'deathball' object, applies damage to the player upon collision.

 var playerObject : GameObject;
 var damage : float = 10f;
 var oldHealth;
 var newHealth;
 
 
 function OnCollisionEnter (col : Collision)
     {
     if (col.gameObject.name == "Player")
         {
         print ("Collision");
         oldHealth = playerObject.GetComponent("Health");
         oldHealth = playerObject.Health.health;
         newHealth = oldHealth - damage;
         playerObject.Health.health = newHealth;
         }
     }
 

My problem is that upon colliding the two objects, I receive this error:

NullReferenceException: Object reference not set to an instance of an object Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.String cacheKeyName, System.Type[] cacheKeyTypes, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.Object[] args, System.String cacheKeyName, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetProperty (System.Object target, System.String name) UnityScript.Lang.UnityRuntimeServices.GetProperty (System.Object target, System.String name) CollisionDamage.OnCollisionEnter (UnityEngine.Collision col) (at Assets/Scripts/Damage/CollisionDamage.js:13)