Not meant for merging.

As of Adwaita 1.5.0, the GTK Box is not being properly unref'd when the
parent window is closed. Update the conditional to account for this.

Also add a couple of missing unref()s in errdefers.

This fixes an issue where Ghostty would not properly quit after closing
the last surface.
https://github.com/ghostty-org/ghostty/discussions/3807 is related
(though I'm not sure it's the exact same problem).

As of Adwaita 1.5.0, the GTK Box is not being properly unref'd when the
parent window is closed. Update the conditional to account for this.

Also add a couple of missing unref()s in errdefers.

It has been done.

It has been done.