Error saying the var is not assigned.

Hi, I’m kind of having a weird problem. All i’m doing is shooting a projectile from the first person camera of the player. I created a prefab which was a red ball and then dragged it into my script that sits on the camera. It works fine, but I get an error that says, “UnassignedReferenceException: The variable theBullet of ‘Shoot Script’ has not been assigned”

#pragma strict

var theBullet : Rigidbody;
var Speed : int ;

function Update () 
	if (Input.GetMouseButtonDown(0))
		var clone = Instantiate(theBullet, transform.position, transform.rotation);
		clone.velocity = transform.TransformDirection(Vector3(0, 0, Speed));
		Destroy (clone.gameObject, 3);

You probably have another instance of the script somewhere that’s throwing the error. That said, you should specify the type of clone, just like you did for your other variables.