Make it legal to have no subnet in --auth-zone, may be contructed instead.

src/option.c

@@ -1587,8 +1587,6 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 	struct auth_zone *new;
 	
 	comma = split(arg);
-	if (!comma)
-	  ret_err(gen_err);
 		
 	new = opt_malloc(sizeof(struct auth_zone));
 	new->domain = opt_string_alloc(arg);