### Godot version

v4.0.beta16.official [518b9e580]

### System information

Windows 10

### Issue description

`RichTextLabel` with `threaded` enabled may crash the game or show the following warning if the node is in another scene:

```
W 0:00:03:0802   test.gd:12 @ load_with_scene(): A Thread object has been re-started without wait_to_finish() having been called on it. Please do so to ensure correct cleanup of the thread.
  <C++ Source>   core/os/thread.cpp:76 @ start()
  <Stack Trace>  test.gd:12 @ load_with_scene()
                 test.gd:6 @ load_items()
                 test.gd:26 @ _on_button_pressed()
```

It may crash the game (without any warning) if it's added directly.

In `v4.0.beta15.official [4fa6edc88]` I was able to reproduce the same warning on my project but I can't reproduce it in the attached MRP. I get a different error and will crash too if the node is added directly:

```
E 0:00:03:0019   remove_from_group: Condition "!E" is true.
  <C++ Source>   scene/main/scene_tree.cpp:157 @ remove_from_group()
```


### Steps to reproduce

Click on the  `Load with scene` or `Load with node` buttons in the attached MRP until it shows a warning/error or crashes. It may take a while.

### Minimal reproduction project

[add_chid_bug_b16.zip](https://github.com/godotengine/godot/files/10521402/add_chid_bug_b16.zip)

return msdfgen::Point2(vector.x / 60.0f, vector.y / 60.0f);
}
static int ft_move_to(const FT_Vector *to, void *user) {
	MSContext *context = static_cast<MSContext *>(user);
	if (!(context->contour && context->contour->edges.empty())) {
		context->contour = &context->shape->addContour();
	}
	context->position = ft_point2(*to);
	return 0;
}
static int ft_line_to(const FT_Vector *to, void *user) {
	MSContext *context = static_cast<MSContext *>(user);
	msdfgen::Point2 endpoint = ft_point2(*to);
	if (endpoint != context->position) {
		context->contour->addEdge(new msdfgen::LinearSegment(context->position, endpoint));
		context->position = endpoint;
	}
	return 0;
}
static int ft_conic_to(const FT_Vector *control, const FT_Vector *to, void *user) {