Menu Script Problem

This menu script had been working perfectly but for some strange reason that I cannot seem to find, whenever I try to run the script, unity gives me two compiler errors:

NullReferenceException: Object reference not set to an instance of an object

menu.Start () (at Assets/menu.js:50)

and

NullReferenceException: Object reference not set to an instance of an object

menu.VolumeControl () (at Assets/menu.js:196)

menu.ShowToolbar () (at Assets/menu.js:138)

menu.OnGUI () (at Assets/menu.js:113)

Here is the code:

 var skin:GUISkin;
  
 private var gldepth = -0.5;
 private var startTime = 0.1;
  
 var mat:Material;
  
 private var tris = 0;
 private var verts = 0;
 private var savedTimeScale:float;
 private var pauseFilter;
  
 private var showfps:boolean;
 private var showtris:boolean;
 private var showvtx:boolean;
 private var showfpsgraph:boolean;
  
 var lowFPSColor = Color.red;
 var highFPSColor = Color.green;
  
 var lowFPS = 30;
 var highFPS = 50;
  
 var start:GameObject;
  
 var url = "unity.html";
  
 var statColor:Color = Color.yellow;
 
 var crediticons:Texture[];
  
 enum Page {
     None,Main,Options
 }
  
 private var currentPage:Page;
  
 private var fpsarray:int[];
 private var fps:float;
  
 function Start() {
     fpsarray = new int[Screen.width];
     Time.timeScale = 1.0;
     pauseFilter = Camera.main.GetComponent(SepiaToneEffect);
     PauseGame();
 }
  
 function OnPostRender() {
     if (showfpsgraph && mat != null) {
         GL.PushMatrix ();
         GL.LoadPixelMatrix();
         for (var i = 0; i < mat.passCount; ++i)
         {
             mat.SetPass(i);
             GL.Begin( GL.LINES );
             for (var x=0; x<fpsarray.length; ++x) {
                 GL.Vertex3(x,fpsarray[x],gldepth);
             }
         GL.End();
         }
         GL.PopMatrix();
         ScrollFPS();
     }
 }
  
 function ScrollFPS() {
     for (var x=1; x<fpsarray.length; ++x) {
         fpsarray[x-1]=fpsarray[x];
     }
     if (fps < 1000) {
         fpsarray[fpsarray.length-1]=fps;
     }
 }
  
 static function IsDashboard() {
     return Application.platform == RuntimePlatform.OSXDashboardPlayer;
 }
  
 static function IsBrowser() {
     return (Application.platform == RuntimePlatform.WindowsWebPlayer ||
         Application.platform == RuntimePlatform.OSXWebPlayer);
 }
  
 function LateUpdate () {
     if (showfps || showfpsgraph) {
         FPSUpdate();
     }
     if (Input.GetKeyDown("p")) {
         switch (currentPage) {
             case Page.None: PauseGame(); break;
             case Page.Main: if (!IsBeginning()) UnPauseGame(); break;
             default: currentPage = Page.Main;
         }
     }
 }
  
 function OnGUI () {
     if (skin != null) {
         GUI.skin = skin;
     }
     ShowStatNums();
     ShowLegal();
     if (IsGamePaused()) {
         GUI.color = statColor;
         switch (currentPage) {
             case Page.Main: PauseMenu(); break;
             case Page.Options: ShowToolbar(); break;
         }
     }    
 }
  
 function ShowLegal() {
     if (!IsLegal()) {
         GUI.Label(Rect(Screen.width-100,Screen.height-20,90,20),
         "carsimulator3d.blogspot.com");
     }
 }
  
 function IsLegal() {
     return !IsBrowser() || 
     Application.absoluteURL.StartsWith("http://www.carsimulator3d.blogspot.com/") ||
     Application.absoluteURL.StartsWith("http://carsimulator3d.blogspot.com/");
 }
  
 private var toolbarInt:int=0;
 private var toolbarStrings: String[]= ["Zoom","Quality","Stats","System","2d/3d"];
  
 function ShowToolbar() {
     BeginPage(300,300);
     toolbarInt = GUILayout.Toolbar (toolbarInt, toolbarStrings);
     switch (toolbarInt) {
         case 0: VolumeControl(); break;
         case 3: ShowDevice(); break;
         case 1: Qualities(); QualityControl(); break;
         case 2: StatControl(); break;
         case 4: Dimension(); break;
     }
     EndPage();
 }
  
 
  
 function ShowBackButton() {
     if (GUI.Button(Rect(20,Screen.height-50,50,20),"Back")) {
         currentPage = Page.Main;
     }
 }
  
  
 function ShowDevice() {
     GUILayout.Label ("Unity player version "+Application.unityVersion);
     GUILayout.Label("Graphics: "+SystemInfo.graphicsDeviceName+" "+
     SystemInfo.graphicsMemorySize+"MB\n"+
     SystemInfo.graphicsDeviceVersion+"\n"+
     SystemInfo.graphicsDeviceVendor);
     GUILayout.Label("Shadows: "+SystemInfo.supportsShadows);
     GUILayout.Label("Image Effects: "+SystemInfo.supportsImageEffects);
     GUILayout.Label("Render Textures: "+SystemInfo.supportsRenderTextures);
 }
  
 function Qualities() {
         GUILayout.Label(QualitySettings.names[QualitySettings.GetQualityLevel()]);
 }
  
 function QualityControl() {
     GUILayout.BeginHorizontal();
     if (GUILayout.Button("Decrease")) {
         QualitySettings.DecreaseLevel();
     }
     if (GUILayout.Button("Increase")) {
         QualitySettings.IncreaseLevel();
     }
     GUILayout.EndHorizontal();
     }
     
 function Dimension() {
     GUILayout.BeginHorizontal();
     if (GUILayout.Button("3D View")) {
         Camera.main.orthographic = false;
     }
     if (GUILayout.Button("2D View")) {
         Camera.main.orthographic = true;
     }
     GUILayout.EndHorizontal();
     }
  
  
 function VolumeControl() {
     GUILayout.Label("Zoom");
     Camera.main.fieldOfView = GUILayout.HorizontalSlider(Camera.main.fieldOfView,100,1.0);
 }
  
 function StatControl() {
     GUILayout.BeginHorizontal();
     showfps = GUILayout.Toggle(showfps,"FPS");
     showtris = GUILayout.Toggle(showtris,"Triangles");
     showvtx = GUILayout.Toggle(showvtx,"Vertices");
     showfpsgraph = GUILayout.Toggle(showfpsgraph,"FPS Graph");
     GUILayout.EndHorizontal();
 }
  
 function FPSUpdate() {
     var delta = Time.smoothDeltaTime;
         if (!IsGamePaused() && delta !=0.0) {
             fps = 1 / delta;
         }
 }
  
 function ShowStatNums() {
     GUILayout.BeginArea(Rect(Screen.width-100,10,100,200));
     if (showfps) {
         var fpsString= fps.ToString ("#,##0 fps");
         GUI.color = Color.Lerp(lowFPSColor, highFPSColor,(fps-lowFPS)/(highFPS-lowFPS));
         GUILayout.Label (fpsString);
     }
     if (showtris || showvtx) {
         GetObjectStats();
         GUI.color = statColor;
     }
     if (showtris) {
         GUILayout.Label (tris+"tri");
     }
     if (showvtx) {
         GUILayout.Label (verts+"vtx");
     }
     GUILayout.EndArea();
 }
  
 function BeginPage(width,height) {
     GUILayout.BeginArea(Rect((Screen.width-width)/2,(Screen.height-height)/2,width,height));
 }
  
 function EndPage() {
     GUILayout.EndArea();
     if (currentPage != Page.Main) {
         ShowBackButton();
     }
 }
  
 function IsBeginning() {
     return Time.time < startTime;
 }
  
  
 function PauseMenu() {
     BeginPage(200,200);
     if (GUILayout.Button (IsBeginning() ? "Play" : "Continue")) {
         UnPauseGame();
  
     }
     if (GUILayout.Button ("Options")) {
         currentPage = Page.Options;
     }
     if (IsBrowser() && !IsBeginning() && GUILayout.Button ("Restart")) {
         Application.OpenURL(url);
     }
     EndPage();
 }
  
 function GetObjectStats() {
     verts = 0;
     tris = 0;
     var ob = FindObjectsOfType(GameObject);
     for (var obj in ob) {
         GetObjectStats(obj);
     }
 }
  
 function GetObjectStats(object) {
     var filters : Component[];
     filters = object.GetComponentsInChildren(MeshFilter);
     for( var f : MeshFilter in filters )
     {
         tris += f.sharedMesh.triangles.Length/3;
           verts += f.sharedMesh.vertexCount;
     }
 }
  
 function PauseGame() {
     savedTimeScale = Time.timeScale;
     Time.timeScale = 0;
     AudioListener.pause = true;
     if (pauseFilter) pauseFilter.enabled = true;
     currentPage = Page.Main;
 }
  
 function UnPauseGame() {
     Time.timeScale = savedTimeScale;
     AudioListener.pause = false;
     if (pauseFilter) pauseFilter.enabled = false;
     currentPage = Page.None;
     if (IsBeginning() && start != null) {
         start.active = true;
     }
 }
  
 function IsGamePaused() {
     return Time.timeScale==0;
 }
  
 function OnApplicationPause(pause:boolean) {
     if (IsGamePaused()) {
         AudioListener.pause = true;
     }
 }

Picture of console

picture of inspector

What happens when I play the game:

I click play

when I click play the game pauses and the first compiler error comes up so I unpause it, and the game works.

When I try to press "options" on my menu - the game stops working and the second compiler error comes up

Help me please! Also - I do realise that the camera zoom slider is referred to in the script as "volume control" - its supposed to be like that.