The scale property tracks the relative size at which we display thumbnails
given the space we have available.
That assumes that the allocation represents that available space, but it will
actually be smaller while the minimap itself is collapsing.
Luckily we have an easy option to avoid a distorted scale: Just don't update
it while collapsing. We expect scale changes when adding or removing thumbnails,
but as we freeze those during transitions, we can do the same with the scale.
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3739
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1696>
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