### 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)

fargs.memory_base = (unsigned char *)p_font_data->data_ptr;
		fargs.memory_size = p_font_data->data_size;
		fargs.flags = FT_OPEN_MEMORY;
		fargs.stream = &fd->stream;
		int max_index = 0;
		FT_Face tmp_face = nullptr;
		error = FT_Open_Face(ft_library, &fargs, -1, &tmp_face);
		if (tmp_face && error 
			max_index = tmp_face->num_faces - 1;
		}
		if (tmp_face) {
			FT_Done_Face(tmp_face);
		}
		error = FT_Open_Face(ft_library, &fargs, CLAMP(p_font_data->face_index, 0, max_index), &fd->face);
		if (error) {
			FT_Done_Face(fd->face);
			fd->face = nullptr;
			memdelete(fd);
			ERR_FAIL_V_MSG(false, "FreeType: Error loading font: '" + String(FT_Error_String(error)) + "'.");
		}
		if (p_font_data->msdf) {
			fd->oversampling = 1.0;
			fd->size.x = p_font_data->msdf_source_size;
		} else if (p_font_data->oversampling <= 0.0) {
			fd->oversampling = _font_get_global_oversampling();
		} else {
			fd->oversampling = p_font_data->oversampling;
		}
		if (FT_HAS_COLOR(fd->face) && fd->face->num_fixed_sizes > 0) {
			int best_match = 0;