need help with flashlight script

i am trying to make a game with a flashlight and the script i am using will say this variable is not assigned and when i add the variable it says it is already assigned. this is the code:
using UnityEngine;
using System.Collections;




public class Flashlight_PRO : MonoBehaviour
{
[Space(10)]
[SerializeField()] GameObject Lights; // all light effects and spotlight
[SerializeField()] AudioSource switch_sound; // audio of the switcher
[SerializeField()] ParticleSystem dust_particles; // dust particles



private Light spotlight;
private Material ambient_light_material;
private Color ambient_mat_color;
private bool is_enabled = false;

// Use this for initialization
void Start ()
{
// cache components
spotlight = Lights.transform.Find ("Spotlight").GetComponent<Light> ();
ambient_light_material = Lights.transform.Find ("ambient").GetComponent<Renderer> ().material;
ambient_mat_color = ambient_light_material.GetColor ("_TintColor");
}






/// <summary>
/// changes the intensivity of lights from 0 to 100.
/// call this from other scripts.
/// </summary>
public void Change_Intensivity(float percentage)
{
percentage = Mathf.Clamp (percentage, 0, 100);


spotlight.intensity = (8 * percentage) / 100;

ambient_light_material.SetColor ("_TintColor", new Color(ambient_mat_color.r , ambient_mat_color.g , ambient_mat_color.b , percentage/2000));
}

 

Please use [ code ][ / code ] tags and tell us exactly what the error message is.