NullReferenceException: Object reference not set to an instance of an object PlayerMovementScript.Up

I get this error message : NullReferenceException: Object reference not set to an instance of an object PlayerMovementScript.Update () (at Assets/PlayerMovementScript.js:6)

And the code is:
MouseLookScript.js:

#pragma strict

var lookSensitivity : float = 5;
@HideInInspector
var yRotation : float;
@HideInInspector
var xRotation : float;
@HideInInspector
var currentYRotation : float;
@HideInInspector
var currentXRotation : float;
@HideInInspector
var yRotationV : float;
@HideInInspector
var xRotationV : float;
var lookSmoothDamp : float = 0.1;

function Update() {

yRotation += Input.GetAxis("Mouse X") * lookSensitivity;
xRotation -= Input.GetAxis("Mouse Y") * lookSensitivity;

xRotation = Mathf.Clamp(xRotation, -90, 90);

currentXRotation = Mathf.SmoothDamp(currentXRotation, xRotation, xRotationV, lookSmoothDamp);
currentYRotation = Mathf.SmoothDamp(currentYRotation, yRotation, yRotationV, lookSmoothDamp);

transform.rotation = Quaternion.Euler(currentXRotation, currentYRotation, 0);
}

PlayerMovementScript.js:
var walkAccelaration : float = 5;
var cameraObject : GameObject;

function Update ()
{
transform.rotation = Quaternion.Euler(0, cameraObject.GetComponent(MouseLookScript).currentYRotation, 0);
rigidbody.AddRelativeForce(Input.GetAxis("Horizontal") * walkAccelaration, 0, Input.GetAxis("Vertical") * walkAccelaration);
}

 

It's probably the cameraObject in your PlayerMovementScript. Drag the camera onto it.

 

I have tried that didn't work

 

Object not set to an instance of an object = what you tried to call doesn't exist. Make sure the component you're calling is on the object, you have the correct object, and there aren't any typos. Then restart unity

 

Does player have a rigidbody on it?
Does cameraObject have a MouseLookScript on it?