regression from commit
commit 9814c1f2ed
use fastparser in SvXMLPropertySetContext subclasses
and add some asserts to find the problems earlier.
Change-Id: Ief64f813f2ef7ec005f682713dadb1be47cbcd15
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/101998
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>