This worked with Saxon but not with libxslt.
(regression from 9d3b39cf9f)
Change-Id: I18e66e6136e4fc73718bbe9c7c4c66fb76be31c3
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/116728
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>