When creating a CiviMail it is possible to select this mailing as a "previous mailing" in the recipients list
When creating a CiviMail it is possible to select this mailing as a "previous mailing" in the recipients list. I have not tested what it does but it makes no sense from a user point of view.
To reproduce just name the mailing and then open the recipients list. In fact before the mailing is named it still shows in the list but with the name "null".