Display units cannot be changed in file without viewbox

Steps to reproduce:

open Inkscape (1.0beta, 0.92.x or 0.92.3)
open centrale.svg
if prompted for conversion, leave the default option
(think that you don't like the ruler units)
try to change File > Document properties: Display units

What happened?

the units reset, the rulers do not change. Sometimes, the unit seems to stick, but the rulers still don't change.

Workaround: change scale or viewbox value and change it back. Afterwards it's possible to change the display units.

What should have happened?

Display units should be changeable anytime.

Inkscape Version and Operating System:

Inkscape Version: 0.92.3, 0.92.4, 1.0beta2
Operating System: Linux Mint 19.2

Edited Dec 04, 2019 by Maren Hachmann

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