The installer outputs an error when <logins> or <metadataDictionary> is present but empty. This is incosistent with the other optional tags (roles, groups, displays, searchForms) which can exist and be empty.
When running the installer with such an xml profile it outputs an error which IMHO is not easy to trace back. Also in the case of an empty <logins> it will create (like with a non-existent <logins>) a default user login.
I suggest to change the @minOccurs of the repective sub-element <xs:element> of logins and metadataDictionary to 0 (now: 1).