In objectValues, doing nothing is a BTree is not initialized speeds up
_setObject by about ~1 %. But a third code path must be added for OFS Folders
(here, ERP5 Category Tool).

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@30252 20353a03-c40f-0410-a6d1-a30d3c3de9de