clean up the plugin a little, and try to catch params which are default
constructed, which doesn't seem to be working yet

Change-Id: Ife45f18502a45cd26306424b7432c55fcbb0fd12
Reviewed-on: https://gerrit.libreoffice.org/28861Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>