Ancient 2.5 UI issue:
The button views in Property Editor have an internal storage, to ensure the view
on the buttons stays same when you switch contextes or select objects.
Bug was that - in case buttons were all scrolled invisible - sometimes no slider
was drawn to indicate that.
Discussion on whether this is a good feature or not: the only improvement would
be to store such settings even per object... but that's a feature creep I think.
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