Robustify PropItem::Read.
Robustify PropItem::Read.

Initialize nType and nItemSize variables in case stream is faulty.

Change-Id: I59602f2b04e3816d8de7cc1a5e7e526c8e822477
Reviewed-on: https://gerrit.libreoffice.org/4762
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