Linea colorata panel con object

Colored line panel with object

Something strange happens to me

maybe another bug

I get the writing [object, object] on the panel line

how to delete the writing?

Then another question:

why the panel line is not white as specified here

{BorderStyle: "white"}

// script

var window = new Window('dialog', 'My Window');
 window .orientation = "column";
panel=  window .add("panel", undefined,{borderStyle:"white"});
window.startButton =panel.add('button', undefined, 'close')
window.startButton.onClick = function() {
 window .close();
}
window.show();