If the user-supplied hostname can't be found then we should not use it.
We already avoid doing that in the non-NO_IPV6 case by checking if the
return value of getaddrinfo() is zero (success). Do the same in the
NO_IPV6 case and make sure the return value of gethostbyname() isn't
NULL before dereferencing this pointer.
Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>