error with Instantiate script

idk why im getting this but i am the error is

NullReferenceException: Object reference not set to an instance of an object

here is the script

var projectile : GameObject;
var spawnpoint: GameObject;

function Update () {
    if (Input.GetButtonDown ("Jump")) {
        Instantiate (projectile, spawnpoint.position, transform.rotation);
    }
}

Presumably, either projectile or spawnpoint haven’t been assigned in the inspector. Make sure you have both of them set up properly.