We can get polypolgons with polygons that have 0 or 1 point only,
so we need to guard agains division-by-zero errors by skipping if
we detect such polygons (as we can't draw them anyway).

Change-Id: Ia27fcde9467864b10572a78a848ea642a3559185
Reviewed-on: https://gerrit.libreoffice.org/31770Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>