fix QPro import filter, related #i41688#

We desperately need a test document for this format.

Change-Id: Ifd8e35bb3330c2b9d2443a3a0f18209001a4bdff
Reviewed-on: https://gerrit.libreoffice.org/8037
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>