Bug 74816 is currently "Return HTTP 404 error, not 500, for non-existent domains" (referring to subdomains-of.launchpad.net). If that HTTP(S)-only change wouldn't solve this problem, perhaps it should instead be "Return NXDOMAIN, not 500, for non-existent domains", in which case this bug should be a duplicate.
Bug 74816 is currently "Return HTTP 404 error, not 500, for non-existent domains" (referring to subdomains- of.launchpad. net). If that HTTP(S)-only change wouldn't solve this problem, perhaps it should instead be "Return NXDOMAIN, not 500, for non-existent domains", in which case this bug should be a duplicate.