### 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 ofs = ((i + tex_pos.y + p_rect_margin * 2) * tex.texture_w + j + tex_pos.x + p_rect_margin * 2) * 4;
					ERR_FAIL_COND_V(ofs >= tex.imgdata.size(), FontGlyph());
					wr[ofs + 0] = (uint8_t)(CLAMP(image(j, i)[0] * 256.f, 0.f, 255.f));
					wr[ofs + 1] = (uint8_t)(CLAMP(image(j, i)[1] * 256.f, 0.f, 255.f));
					wr[ofs + 2] = (uint8_t)(CLAMP(image(j, i)[2] * 256.f, 0.f, 255.f));
					wr[ofs + 3] = (uint8_t)(CLAMP(image(j, i)[3] * 256.f, 0.f, 255.f));
				}
			}
		}
		tex.dirty = true;
		chr.texture_idx = tex_pos.index;
		chr.uv_rect = Rect2(tex_pos.x + p_rect_margin, tex_pos.y + p_rect_margin, w + p_rect_margin * 2, h + p_rect_margin * 2);
		chr.rect.position = Vector2(bounds.l - p_rect_margin, -bounds.t - p_rect_margin);
		chr.rect.size = chr.uv_rect.size;
	}
	return chr;
}
#endif
#ifdef MODULE_FREETYPE_ENABLED
_FORCE_INLINE_ TextServerAdvanced::FontGlyph TextServerAdvanced::rasterize_bitmap(FontForSizeAdvanced *p_data, int p_rect_margin, FT_Bitmap bitmap, int yofs, int xofs, const Vector2 &advance, bool p_bgra) const {
	int w = bitmap.width;
	int h = bitmap.rows;
	int color_size = 2;
	switch (bitmap.pixel_mode) {
		case FT_PIXEL_MODE_MONO:
		case FT_PIXEL_MODE_GRAY: {
			color_size = 2;
		} 
		case FT_PIXEL_MODE_BGRA: {
			color_size = 4;