I have specific wp menus for each url.
When I encounter a url that has no matching wp menu I dont want any nav. So far it seems if none is found it will show a default nav or pick one of the existing navs to show.
http://domainnameA.com show wp_nav_menu('domainnameA')
http://domainnameB.com no menu exists - dont show a nav
instead I am getting Nav on Domain B that has a link to the only page that exists. If I delete the page I get no navigation but that is not a great solution.