How to move the main camera in Google Cardboard?

I am working with Google Cardboard and I need to make it so that when the user looks at an object with the tag "End" the main camera will move along a ray toward that object. I have some code but my if statement is a null reference so it doesn't work. below is my code any help would be greatly appreciated.

public class RaycastScript : MonoBehaviour {

 public Camera camera;
 public float moveSpeed;
 
 // Update is called once per frame
 void FixedUpdate () {
 //    Vector3 fwd = transform.TransformDirection(Vector3.forward);
 //    Physics.Raycast (transform.position, fwd, 60);  
     RaycastHit hit;
     if (hit.collider.tag == "End") {
         Ray ray = camera.ScreenPointToRay (Input.mousePosition);
         camera.transform.Translate (ray.direction * moveSpeed, Space.Self);
     }
 }

}