Bug description

I was documenting the basics of creating a Popochiu game when I discovered that the player character is not automatically added to the first room when the game is run.

This seems an unwanted behavior since explicitly adding the main character to each room in the game is redundant.

Steps to reproduce

Either follow the "Creating game stub" guide on the official documentation or:

1. Start from a fresh project
2. Create a single character named Goddiu and set it as the player character (assign a sprite so you can view it)
3. Create a single room named House and set it as the main scene (no need for walkable areas or anything)
4. Run the game

Expected vs observed behavior

I would expect the game to run normally, with the main character stuck in the middle of the room (in the absence of WAs).

The observed behavior is the game hangs on an empty room, with this error in the debugger:

Environment information (please complete):

• Godot version: 4.2
• Plugin version or branch: develop (0963cc8f6169dc commit hash)

Additional context

To make things work, it suffices to explicitly add the main character as one of the room characters.