Properly handle invalid room references in savefiles. In all games, rs_write_room_reference() stored -1 for a nonexistent room, but rs_read_room_reference() did not check for out-of-bounds values, leading to pointers to rooms[-1], which sometimes caused crashes. rs_read_room_reference() has now been modified to use NULL instead. Some of the games required further changes to replace NULL with the pointer to the actual room. Others are capable of handling NULL for objects not in any room.

/* 
 * Networking information -- should not vary among networking machines
 *
 * Advanced Rogue
 * Copyright (C) 1984, 1985 Michael Morgan, Ken Dalka and AT&T
 * All rights reserved.
 *
 * See the file LICENSE.TXT for full copyright and licensing information.
 */

#define SYSLEN 9
#define LOGLEN 8
#define NUMNET 6
#undef NUMNET
struct network {
    char *system;
    char *rogue;
};
extern struct network Network[];

/* This system's name -- should not be defined if uname() is available */