Unable to add exported TileMapLayer property to scene node

### Tested versions

- Reproducable v4.3.stable.mono.official [77dcf97d8]

### System information

Both Mac and PC

### Issue description

Attempting to drag&drop a TileMapLayer onto a scene node property won't take.

If I add it to the tscn file directly it's removed on build.

(I'm new to godot so might not be describing this properly)

### Steps to reproduce

I'm following a tutorial on udemy. But here's a screenshot


### Minimal reproduction project (MRP)

[puzzle_course.zip](https://github.com/user-attachments/files/17376788/puzzle_course.zip)

Start by opening the attached puzzle_course.zip minimal reproduction project in Godot v4.3.stable.mono.official and reproducing the failed drag-and-drop assignment to the TileMapLayer scene-node property. Inspect the exported property and the relevant .tscn scene data; done means the property can be assigned in the editor and is retained when the project is built.

Written by the indexing model from the issue text.