In 5c9ccd4351c97426d3768b5530ae6eb2c1c7f7b3, the directory
/usr/share/themes/Kali-Light/gtk-3.0/assets became a symlink.
Such a change requires an explicit intervention in the packaging files.
From dpkg-maintscript-helper(1):
> SYMLINK AND DIRECTORY SWITCHES
> When upgrading a package, dpkg will not automatically switch a symlink
> to a directory or vice-versa.
Issue initially reported at https://bugs.kali.org/view.php?id=7182
