Help with NullReferenceException

 var H00 : Texture2D;
 var H10 : Texture2D;
 var H20 : Texture2D;
 var H30 : Texture2D;
 var H40 : Texture2D;
 var H50 : Texture2D;
 var H60 : Texture2D;
 var H70 : Texture2D;
 
 var MAX_HEALTH = 70;
 var HEALTH = 70;
 function Update()
 {
     var g_Health = GameObject.Find("g.Health");
     if(HEALTH > MAX_HEALTH){
     HEALTH = MAX_HEALTH;
     }
     if(HEALTH > 60){
     g_Health.guiTexture.texture = H70;
     }
     else if(HEALTH > 50){
     g_Health.guiTexture.texture = H60;
     }
     else if(HEALTH > 40){
     g_Health.guiTexture.texture = H50;
     }
     else if(HEALTH > 30){
     g_Health.guiTexture.texture = H40;
     }
     else if(HEALTH > 20){
     g_Health.guiTexture.texture = H30;
     }
     else if(HEALTH > 10){
     g_Health.guiTexture.texture = H20;
     }
     else if(HEALTH > 0){
     g_Health.guiTexture.texture = H10;
     }
     else if(HEALTH <= 0){
     g_Health.guiTexture.texture = H00;
         return;
     }
 }

from this javascript I get this error NullReferenceException Health.Update () (at Assets/Scripts/Health.js:19) and I have no idea why PLEASE HELP