fix potential hang here

Change-Id: Id62cdb90420b9ccf4e98fc1af46c70db6ed60ee0

vcl/source/filter/wmf/winwmf.cxx

@@ -1735,9 +1735,14 @@ bool WMFReader::GetPlaceableBound( Rectangle& rPlaceableBound, SvStream* pStm )
                 }
                 break;
             }
+
+            const sal_uInt32 nAvailableBytes = nEnd - nPos;
+            const sal_uInt32 nMaxPossibleRecordSize = nAvailableBytes/2;
+            if (nRSize <= nMaxPossibleRecordSize)
+            {
                 nPos += nRSize * 2;
-             if ( nPos <= nEnd )
                 pStm->Seek( nPos );
+            }
             else
             {
                 pStm->SetError( SVSTREAM_FILEFORMAT_ERROR );