I destroyed a Popup set as modal, and the Overlay.modal object remains displayed. This issue occurs whether using a custom overlay or the default one. I've tested versions 5.15.2, 6.5.1, and 6.5.2, and this issue doesn't exist in them. If I first close it and then destroy it, everything works as expected. However, in actual software development, we can't guarantee that it will always go through the close process.

Using test code, you can see that after clicking once, the popup will open, and then after clicking again, it will close. The expected behavior is to return to a completely black interface. However, in version 6.5.3, the green overlay remains.