avoid buffer overflow by using wrong buffer
avoid buffer overflow by using wrong buffer

Found by Asan.

(regression from CWS mba34issues01)

Change-Id: Ia7159c9bed9d7f823448acd02e18568a5f3f2093
Reviewed-on: https://gerrit.libreoffice.org/10717
Reviewed-by: Michael Stahl <eef8671db506f9731c0438a7613853b6391ca841@redhat.com>
Tested-by: Michael Stahl <eef8671db506f9731c0438a7613853b6391ca841@redhat.com>

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core