check seek succeeded

Change-Id: Idd8f0c02e266086f069dd9e3f7f4b8944f2859d3
Reviewed-on: https://gerrit.libreoffice.org/43667Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

filter/source/msfilter/msdffimp.cxx

@@ -6179,7 +6179,8 @@ bool SvxMSDffManager::GetShapeContainerData( SvStream& rSt,
         }
         else
         {
-            rSt.SeekRel( nLength );
+            if (!checkSeek(rSt, rSt.Tell() + nLength))
+                return false;
             nReadSpCont += nLength;
         }
     }