### 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)

fd->glyph_map[p_glyph] = FontGlyph();
				ERR_FAIL_V_MSG(false, "FreeType: Failed to load glyph stroker.");
			}
			FT_Stroker_Set(stroker, (int)(fd->size.y * fd->oversampling * 16.0), FT_STROKER_LINECAP_BUTT, FT_STROKER_LINEJOIN_ROUND, 0);
			FT_Glyph glyph;
			FT_BitmapGlyph glyph_bitmap;
			if (FT_Get_Glyph(fd->face->glyph, &glyph) != 0) {
				goto cleanup_stroker;
			}
			if (FT_Glyph_Stroke(&glyph, stroker, 1) != 0) {
				goto cleanup_glyph;
			}
			if (FT_Glyph_To_Bitmap(&glyph, aa_mode, nullptr, 1) != 0) {
				goto cleanup_glyph;
			}
			glyph_bitmap = (FT_BitmapGlyph)glyph;
			gl = rasterize_bitmap(fd, rect_range, glyph_bitmap->bitmap, glyph_bitmap->top, glyph_bitmap->left, Vector2(), bgra);
		cleanup_glyph:
			FT_Done_Glyph(glyph);
		cleanup_stroker:
			FT_Stroker_Done(stroker);
		}
		fd->glyph_map[p_glyph] = gl;
		return gl.found;
	}
#endif
	fd->glyph_map[p_glyph] = FontGlyph();
	return false;
}
_FORCE_INLINE_ bool TextServerAdvanced::_ensure_cache_for_size(FontAdvanced *p_font_data, const Vector2i &p_size) const {