Help with Inventory Script

Hello, I made this inventory script for my game. It works great but has one bug.. Somtimes when i pick up an item it duplicates in my inventory... #pragma strict var hand : GameObject;

 var sword : Texture;
 var shovel : Texture;
 var woodBlock : Texture;
 var windowBlock : Texture;
 var stoneBlock : Texture;
 var nukeTex : Texture;
 static var nuke : Texture;
 
 
 
 var blank : Texture;
 
 var house : GUISkin;
 private var inventoryOpen : boolean;
 private var gridValue : float = 0;
 
 
 var inventoryTex : Texture;
 var Grids : Texture[];
 
 function Start () {
 nuke = nukeTex;
 }
 
 function Update () {
     if(Input.GetKeyUp("i")){
         if(inventoryOpen == false){
         inventoryOpen = true;
         }
         else if(inventoryOpen == true){
         inventoryOpen = false;
         }
     }
 }
 
 function OnGUI(){
 GUI.skin = house;
 if(inventoryOpen == true){
       GUI.BeginGroup (new Rect (0,0,360,360),inventoryTex);
       //grid
       gridValue = GUI.SelectionGrid(Rect(30,30,300,300), gridValue,Grids,5);
       
       
       //Apply Sword
       if(Grids[gridValue] == sword){
       PlayerDamge.tool = 2;
       hand.renderer.material.mainTexture = sword;
       AddBlock.level = 1;
       }
       
       //Apply Shovel
       if(Grids[gridValue] == shovel){
       PlayerDamge.tool = 1;
       hand.renderer.material.mainTexture = shovel;
       Debug.Log("Shovel");
       }
       
       //Apply Wood Block
       if(Grids[gridValue] == woodBlock){
       PlayerDamge.tool = 3;
       hand.renderer.material.mainTexture = woodBlock;
       AddBlock.blockTex = woodBlock;
       }
       //Apply windowBlock
       if(Grids[gridValue] == windowBlock){
       PlayerDamge.tool = 3;
       hand.renderer.material.mainTexture = windowBlock;
       AddBlock.blockTex = windowBlock;
             Debug.Log("Window");
             }
             
        //Apply stoneBlock
       if(Grids[gridValue] == stoneBlock){
       PlayerDamge.tool = 3;
       hand.renderer.material.mainTexture = stoneBlock;
       AddBlock.blockTex = stoneBlock;
       }
         //Apply nuke
       if(Grids[gridValue] == nuke){
       PlayerDamge.tool = 3;
       hand.renderer.material.mainTexture = nuke;
       AddBlock.blockTex = nuke;
       }
 
       
       GUI.EndGroup();
       }
 }
 
 
 function OnTriggerEnter (c : Collider){
     if(c.tag == "Item"){
         //Sword
         if(c.renderer.material.mainTexture == sword){
         AddItem(sword);
         Destroy(c.gameObject);
         }
         //Shovel
         if(c.renderer.material.mainTexture == shovel){
         AddItem(shovel);
         Destroy(c.gameObject);
         }
         //Wood Block
         if(c.renderer.material.mainTexture == woodBlock){
         AddItem(woodBlock);
         Destroy(c.gameObject);
         }
         //windowBlock
         if(c.renderer.material.mainTexture == windowBlock){
         AddItem(windowBlock);
         Destroy(c.gameObject);
         }
         //stoneBlock
         if(c.renderer.material.mainTexture == stoneBlock){
         AddItem(stoneBlock);
         Destroy(c.gameObject);
         }
         //nuke
         if(c.renderer.material.mainTexture == nuke){
         AddItem(nuke);
         Destroy(c.gameObject);
         }
     }
 }
 
 function AddItem (itemTex : Texture){
     var i :int;
     for(i=0;i<25;i++){
         if(Grids[i] == blank){
         Grids[i] = itemTex;
         i = 26;
         break;
         }
     }
     
 }

Thanks!, MileSplit