We currently have two components that show or hide the minimap:
- the thumbnails hide themselves in case of a single static workspace
- overview controls show the minimap when no search is active
That obviously doesn't work correctly.
To fix this, change thumbnails to set a new :should-show property instead
of the visibility, and let the overview controls take it into account
when changing the visibility.
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3739
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1696>