astats IPv6 and IPv4 access list behavior inconsistency

The behavior of the access configuration parameter for astats is inconsistent. When allow_ip is present with no arguments, or is missing, requests into astats are denied with a 404 not found. The allow_ip6 parameter is the opposite. When present with no arguments, or missing, requests into astats are served. When an IP list is present in either case, access is denied unless one's source address is within the specified list of subnets.