Describe the bug
Context: Migrating a project from v3 to v4.
Merging a room let myroom = rooms.merge(roomName); causes the error:
Uncaught Error: [ct.tiles] Attempt to cache an already cached tilemap.

To Reproduce

1. Use rooms.merge()
   Bug happens on the first call.
   Game crashes. Error message seen in debug console.

   Uncaught Error: [ct.tiles] Attempt to cache an already cached tilemap.
   at Tilemap.cache (ct.js:1334:15)
   at Object.merge (ct.js:3847:12)
   at _Room.onCreate (ct.js:8799:23)

Expected behavior
rooms.merge creates a new merged room.

System information report
Ct.js v4.0.1 😽 (packaged)

NW.JS v0.72.0
Chromium v109.0.5414.87
Node.js v19.3.0
Pixi.js v7.3.2

WebGPU UNAVAILABLE
WebGL available
WebGL vendor Google Inc. (Intel)
WebGL renderer ANGLE (Intel, Vulkan 1.3.255 (Intel(R) Xe Graphics (TGL GT2) (0x00009A49)), Intel open-source Mesa driver)
OS linux x64 // Linux 6.5.0-18-generic