remove ListBox item's icon?

I'm trying to remove the listbox item's icon or image, but nothing seems to work?! What am I doing wrong?

    var w = new Window ("window");
    lb = w.add ("listbox", [0,0,100,150], ["item1", "item2", "item3"]);
    var btn = w.add ("button");
    
    lb.items[1].icon = File ("~/Desktop/redSquare.jpg");
    
    // None of this is working... 
    btn.onClick = function (){
        lb.items[1].icon.remove();
        lb.items[1].image.remove();
        lb.items[1].remove("icon");
        lb.items[1].remove("image");
        lb.remove("image", items[1]);
        lb.remove("icon", items[1]);
        lb.remove(items[1].icon);
        lb.remove(items[1].image);
        }
    
    w.show();