crash in numbering on/off->more numbering

regression from

commit 2fa44119
Author: Tomaž Vajngerl <tomaz.vajngerl@collabora.co.uk>
Date:   Mon May 11 17:55:36 2015 +0900

    refactor ValueSet to use RenderContext

    Change-Id: I3985804f8cfd1b6807bc02bef5af3e24e5cb3cbf

don't know if the Invalidate that replaced this ImplInitScrollBar call
is actually necessary of not.

Change-Id: I6aff171af6b7294a28f3b68fe854f25f51b6b70a

svtools/source/control/valueset.cxx

@@ -2265,6 +2265,7 @@ long ValueSet::GetScrollWidth() const
     if (GetStyle() & WB_VSCROLL)
     {
         const_cast<ValueSet*>(this)->Invalidate();
+        const_cast<ValueSet*>(this)->ImplInitScrollBar();
         return mxScrollBar->GetSizePixel().Width() + SCRBAR_OFFSET;
     }
     else