Can't add characters to more than one room (1.x)

[mapedorr]

Bug description

Using the + Add character to room button in the Characters in room category of the Room tab shows characters already added to another opened room scene disabled.

Steps to reproduce

Steps to reproduce the behavior:

1. In the maintenance/1.x branch open the 101 room.
2. Then open the Outside room.
3. In the Outside room, click on the + Add character to room button in the Characters in room category.
4. The character Popsy will appear as disabled even if not present in the room.

Expected vs observed behavior

Characters that are not in the room should be enabled to be added through the + Add character to room button in the Characters in room category.

Environment information (please complete):

• OS type and version: Windows 11
• Godot version: 3.5.3
• Plugin version or branch: 1.10.0

Additional context

These are the characters in the 101 room:

The characters appear disabled in the Outside room dispite not being childs of the Characters node:

[mapedorr]

Fixed in #155