APOORV SACHAN authored Jun 10, 2020 and António Fernandes committed Jun 12, 2020

The GtkImage that displays the window icon may or may not be contained
by a GtkButton, depending on whether we were able to set a custom icon.

In GtkBuilder UI definitions we cannot do this anymore, as we have to
set a parent for the image widget from the start.

So, define both a simple image and a button with an image, and pack
them in a GtkStack to only show the button when appropriate.