Image remain invisible but wanted it to become visible

The code is currently connected to a NGUI button. It works fine, but the only issue I have is when I clicked on the 3D model button and then clicked on another NGUI button, the showImage remain false.

Therefore, when I clicked back to the original NGUI button, the showImage is blank, but I want it to be visible automatically.

How can I have the showImage going back to true automatically once I return to the original NGUI button? I hope that make sense.

 #pragma strict
     var images : Texture2D[];
     var i : int = 0;
     var showImage = true;
     public var objectToHide:GameObject;
     
     function Start(){
         if(showImage == false){
             showImage = true;
         }
     }
   
     function OnGUI () {
         if (showImage)
             GUI.DrawTexture(Rect(365,20,1500,900),images[i]);
               
         if (GUI.Button(new Rect(880,930,100,50),"PREVIOUS"))
         {
             if (i > 0)
                 i--;
      
             GUI.DrawTexture(Rect(200,50,100,100), images[i]);
             print(i);  
             showImage = true;
             objectToHide.SetActive(false);
         }
    
         if (GUI.Button(new Rect(1000,930,100,50),"NEXT"))
         {
             if (i < images.Length - 1)
                 i++;
 
             GUI.DrawTexture(Rect(200,50,100,100), images[i]);  
             print(i);
             showImage = true;
             objectToHide.SetActive(false); 
         }
         if (GUI.Button(new Rect(1120,930,100,50),"3D MODEL"))
     
         {
             showImage = false;
             objectToHide.SetActive(true);            
         }
     }