This takes over the fix from the KDE5FilePicker
from commit 1af4ab72
for the qt5 one.

Change-Id: Ibe34ecff9913fc91df2b9bd25b559375bab0ff83
Reviewed-on: https://gerrit.libreoffice.org/67385
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>