Fixes CVE-2019-7317.

Change-Id: I3374f5cbd6552e2c1569d63ee680d0c1d9389621
Reviewed-on: https://gerrit.libreoffice.org/71663
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit e2abbc00)