crashtesting: set document reference only once
For SdtHelper we need to keep valid reference to main document
(in our case first call), not to any of substreams like header,
footer, etc.
Change-Id: Id9d99c1a9bff9a3392eea4cc6e2abe774e5868d2
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/127672
Tested-by: Jenkins
Reviewed-by: Vasily Melenchuk <vasily.melenchuk@cib.de>
(cherry picked from commit
923665ac525e8dad218724327fdbd98d4fb790ad)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/127581
Reviewed-by: Thorsten Behrens <thorsten.behrens@allotropia.de>