Refresh the prev object after a create, and the prev/next objects
after a delete.  There is no attempt to keep things in sync when
doing a delete by index.  I suppose I *could* (at least theoretically)
do a sync for delete-by-unique-index, but as I can't do it for
delete-by-duplicate-index, I'm just not going to bother at all.  You'll
just have to refresh your data sets after doing anything other than
an object create/delete.