Null references elements, introduced throw

Change-Id: I22bf7de5f20c3ca455df31de2a5d7301b436ed82
Reviewed-on: https://gerrit.libreoffice.org/21691Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>