Object reference not set to an instance of an object?

My script:

 #pragma strict
    var Menus : float = 0;
    var image : Texture2D;
    function Start ()
    	Menus += Time.deltaTime;
    function Update () 
    	GUI.DrawTexture(new Rect(0, 0, image.width, image.height), image);

My error:

NullReferenceException: Object reference not set to an instance of an object
UnityEngine.GUI.DrawTexture (Rect position, UnityEngine.Texture image, ScaleMode scaleMode, Boolean alphaBlend, Single imageAspect) (at C:/BuildAgent/work/cac08d8a5e25d4cb/Runtime/ExportGenerated/Editor/GUI.cs:202)
UnityEngine.GUI.DrawTexture (Rect position, UnityEngine.Texture image) (at C:/BuildAgent/work/cac08d8a5e25d4cb/Runtime/ExportGenerated/Editor/GUI.cs:198)
1st Menus.Update () (at Assets/1st Menus.js:13)

You haven’t snapped in a texture in the editor?
The other option is to ‘Find’ the texture in Start()