In addition to checking if the provided port is numeric, also check
that the string isn't empty and that the port number is within the
valid range. Incidentally, this silences a compiler warning about
ignoring strtol's return value.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx> Signed-off-by: Junio C Hamano <gitster@pobox.com>