make it a little smarter in dealing with fields that are smart pointers

Change-Id: I44072105170882dc29fb19558f1065cffc7e5f11
Reviewed-on: https://gerrit.libreoffice.org/37751Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>