add new 404 handler setting
add new 404 handler setting

frontrowed/wai,kazu-yamamoto/wai,tolysz/wai,erikd/wai,utdemir/wai,erikd/wai,creichert/wai,frontrowed/wai,rgrinberg/wai,rgrinberg/wai,utdemir/wai,erikd/wai,tolysz/wai,frontrowed/wai,rgrinberg/wai,creichert/wai,sordina/wai,yesodweb/wai,sordina/wai,sordina/wai,frontrowed/wai,rgrinberg/wai,kazu-yamamoto/wai,erikd/wai,sordina/wai,utdemir/wai,rgrinberg/wai,utdemir/wai,tolysz/wai,tolysz/wai,yesodweb/wai