Game without an "A" room

[ErinCall]

I want to make a game without an A room, but I get an error when I try to create a map from that. I'm running the exact example code from the README on this game.json:

{
  "rooms": [
    {
      "name": "Z",
      "north": "D",
      "east": "B",
      "south": null,
      "west": null
    },
    {
      "name": "B",
      "north": "E",
      "east": "C",
      "south": null,
      "west": "Z",
      "entrance": "south"
    },
    {
      "name": "C",
      "north": null,
      "east": null,
      "south": null,
      "west": "B"
    },
    {
      "name": "D",
      "north": "G",
      "east": null,
      "south": "Z",
      "west": null
    },
    {
      "name": "E",
      "north": null,
      "east": "F",
      "south": "B",
      "west": null
    },
    {
      "name": "F",
      "north": null,
      "east": null,
      "south": null,
      "west": "E"
    },
    {
      "name": "G",
      "north": "H",
      "east": null,
      "south": "D",
      "west": null
    },
    {
      "name": "H",
      "north": null,
      "east": "I",
      "south": "G",
      "west": null
    },
    {
      "name": "I",
      "north": null,
      "east": "J",
      "south": null,
      "west": "H"
    },
    {
      "name": "J",
      "north": null,
      "east": "K",
      "south": null,
      "west": "I"
    },
    {
      "name": "K",
      "north": null,
      "east": null,
      "south": null,
      "west": "J",
      "treasure": true
    }
  ]
}