Change.js

// change this https://github.com/LearnBoost/socket.io/blob/master/lib/manager.js#L469

if (this.roomClients[id]) {
    for (var room in this.roomClients[id]) {
      this.rooms[room].splice(this.rooms[room].indexOf(id), 1);
    }
  }


// to

if (this.roomClients[id]) {
  for (var room in this.roomClients[id]) {
    this.onLeave(id, room);
  }
  delete this.roomClients[id]
}

onLeave

// change
Manager.prototype.onLeave = function (id, room) {
  if (this.rooms[room]) {
    var index = this.rooms[room].indexOf(id);

    if (index >= 0) {
      this.rooms[room].splice(index, 1);
    }
    delete this.roomClients[id][room];
  }
};

// to

Manager.prototype.onLeave = function (id, room) {
  if (this.rooms[room]) {
    var index = this.rooms[room].indexOf(id);

    if (index >= 0) {
      this.rooms[room].splice(index, 1);
    }

    if (!this.rooms[room].length) {
      delete this.rooms[room];
    }
    delete this.roomClients[id][room];
  }
};