update the plugin to check all methods for deleting fields.

Also remove the dead checks for new failing here, can never have worked,
because it is not calling the std::nothrow variant.

Change-Id: I139410e42f83ae2db0cd38ceee81c8b4c310268c
Reviewed-on: https://gerrit.libreoffice.org/52881Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>