### 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)

int diff = ABS(fd->size.x - ((int64_t)fd->face->available_sizes[0].width));
			fd->scale = double(fd->size.x * fd->oversampling) / fd->face->available_sizes[0].width;
			for (int i = 1; i < fd->face->num_fixed_sizes; i++) {
				int ndiff = ABS(fd->size.x - ((int64_t)fd->face->available_sizes[i].width));
				if (ndiff < diff) {
					best_match = i;
					diff = ndiff;
					fd->scale = double(fd->size.x * fd->oversampling) / fd->face->available_sizes[i].width;
				}
			}
			FT_Select_Size(fd->face, best_match);
		} else {
			FT_Set_Pixel_Sizes(fd->face, 0, double(fd->size.x * fd->oversampling));
			fd->scale = ((double)fd->size.x * fd->oversampling) / (double)fd->face->size->metrics.y_ppem;
		}
		fd->hb_handle = hb_ft_font_create(fd->face, nullptr);
		fd->ascent = (fd->face->size->metrics.ascender / 64.0) / fd->oversampling * fd->scale;
		fd->descent = (-fd->face->size->metrics.descender / 64.0) / fd->oversampling * fd->scale;
		fd->underline_position = (-FT_MulFix(fd->face->underline_position, fd->face->size->metrics.y_scale) / 64.0) / fd->oversampling * fd->scale;
		fd->underline_thickness = (FT_MulFix(fd->face->underline_thickness, fd->face->size->metrics.y_scale) / 64.0) / fd->oversampling * fd->scale;
#if HB_VERSION_ATLEAST(3, 3, 0)
		hb_font_set_synthetic_slant(fd->hb_handle, p_font_data->transform[0][1]);
#else
#ifndef _MSC_VER
#warning Building with HarfBuzz < 3.3.0, synthetic slant offset correction disabled.
#endif
#endif
		if (!p_font_data->face_init) {
			
			if (fd->face->family_name != nullptr) {