Trying to get my enemy attack damage to work

Questions & Answers
1

Hey everybody I amtrying to get my enemy damage to work. I have my player to attack the enemy, and when he attacks the enemy he should die. I dont have any animation set up for the death, I just want the enemy to be destroyed. So far I have this

// sound clips: var struckSound : AudioClip;

var health = 3;

function ApplyDamage( amount : int ) {

health -= amount;
// <- (update on-screen health displays here)

if (health < 0) {
    Die(); 
} 
else {
    // <- (play "hurt" animation & sound here)
    //audio.PlayOneShot(struckSound);

    }

}

function Die() {

// now remove this gameObject from the scene:
Destroy(gameObject);

}

when I attack the enemy the editor stops and gives me the error the prefab you want to instantiate is null. What does this mean? I get this error everytime a run it.

2

Here's the scripts i use i hope they can help

Here's the PlayerHealth script but it has GUI problems:

var maxHealth : int  = 100;
var curHealth : int  = 100;

var healthBarLength : float ;

// Use this for initialization
function Start () {
    healthBarLength = Screen.width / 2;
}

// Update is called once per frame
function Update () {
    AddjustCurrentHealth(0);

}

function OnGUI() {
    GUI.Box(new Rect(10, 10, healthBarLength, 20), curHealth + "/" + maxHealth);
}

function AddjustCurrentHealth(adj) {
    curHealth += adj;

    if(curHealth < 0)
        curHealth = 0;

    if (curHealth > maxHealth)
        curHealth = maxHealth;

    if(maxHealth < 1)
        maxHealth = 1;

    healthBarLength = (Screen.width / 2) * (maxHealth / curHealth);
}

and here's the EnemyAttack:

var target : GameObject;
var attackTimer : float = 2;
var coolDown : float = 2;
var damage : int = 10;

// Use this for initialization
function Start () {
    attackTimer = 0;
    coolDown = 2.0f;

}

// Update is called once per frame
function Update () {
    if(attackTimer > 0)
        attackTimer -= Time.deltaTime;

    if (attackTimer < 0)
        attackTimer = 0;

    if(attackTimer == 0){
        Attack();
        attackTimer = coolDown;
    }
}
function Attack() {
    var distance = Vector3.Distance(target.transform.position, transform.position);

    var direction = Vector3.Dot(target.transform.position - transform.position, transform.forward);

    if(distance < 3) {
        if(direction > 0) {
            var go = GameObject.Find("Player");
            go.GetComponent(PlayerHealth).AddjustCurrentHealth(-damage);
        }
    }
}