Just installed and the main domain has disappear from choosing on registration

Hi all, i just installed the multi-domains plugin, also i didn't have started any configs yet, i just went now after the installation to signup page and the main domain that im using is not listed to choose for using with a blog, it shows just the dot which was separating the sub domain field from the domain field before.
Is it normal when i just have 1 domain ?

Also i didn't have added any other domain yet, im still waiting for the DNS to propagate cause i just have changed the DNS settings for the second domain i want to add.