not of the gradient. Therefore don't reset selection in the gradient
list if step increment changes.
This hopefully fixes also the failing UI test

Change-Id: Ia3da23d80ee9601b40309a2f213bd3b2c850ff5a
Reviewed-on: https://gerrit.libreoffice.org/36508Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>