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)

// Its not able to recognize the health script because of the double quotes.

Change OnCollision to this ,

 var HealthRefScript;

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