checking for casting to void* turns out to mask useful stuff, so
remove that and just deal with a few extra false+

Change-Id: Id9700d7ceda90ba8fdb38aa870f13a7ca3acb668
Reviewed-on: https://gerrit.libreoffice.org/63145
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>