avoid hang in certain ppts

Change-Id: Iedba71b72fc815b274ca5e0da0903a558947cb06
(cherry picked from commit 90dc4e38)
Reviewed-on: https://gerrit.libreoffice.org/18089Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

sd/source/filter/ppt/pptin.cxx

@@ -2544,7 +2544,7 @@ SdrObject* ImplSdPPTImport::ProcessObj( SvStream& rSt, DffObjData& rObjData, voi
             DffRecordHeader& rHdClientData = *maShapeRecords.Current();
             while( true )
             {
-                sal_uInt32 nClientDataLen = rHdClientData.GetRecEndFilePos();
+                sal_uInt32 nClientDataLen = SanitizeEndPos(rSt, rHdClientData.GetRecEndFilePos());
                 DffRecordHeader aHd;
                 do
                 {