Car Audio c# script not working

As a last resort you can put a

var myCamera : Camera;

in the globals and drag and drop a camera to the script after clicking the gameobject and use that variable instead.

I may have slightly derped whilst writing this, as the line the error points to is line 90, but the error in the console is irrelevant to it in the script, "NullReferenceException: Object reference not set to an instance of an object UnityStandardAssets.Vehicles.Car.CarAudio.Update () (at Assets/Standard Assets/Vehicles/Car/Scripts/CarAudio.cs:90)" Is what the error message, but the line it points to is this: float camDist = (Camera.main.transform.position - transform.position).sqrMagnitude; I have no idea what to do to fix this at all