fix crash on loading ooo83574-1.doc

Change-Id: Ia959dde8bac2d663cf1a5bec0358ee89dcaf42ed
(cherry picked from commit 17ccc09ec27bde00e5ed7a9fe6055a991992b0ed)
Reviewed-on: https://gerrit.libreoffice.org/11038
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>