I can only imagine the weird bugs that must have periodically resulted
when we had a hash value collision.
In the process, fix hasElements() to return a useful value

Change-Id: I1d9a052e73332b4b2bbc9c1fd8142c13eb22f1be
Reviewed-on: https://gerrit.libreoffice.org/40226Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>