Skip intercept value if it is near 1

Change-Id: Ie52b2ac06c53c2e85b3c465be28081f6dc0ad2cb
Reviewed-on: https://gerrit.libreoffice.org/19038Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>