### 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)

#endif
#endif
					ftr["type"] = _get_tag_type(feature_tags[i]);
					ftr["hidden"] = _get_tag_hidden(feature_tags[i]);
					p_font_data->supported_features[feature_tags[i]] = ftr;
				}
				memfree(feature_tags);
			}
			
			p_font_data->supported_varaitions.clear();
			if (fd->face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS) {
				FT_MM_Var *amaster;
				FT_Get_MM_Var(fd->face, &amaster);
				for (FT_UInt i = 0; i < amaster->num_axis; i++) {
					p_font_data->supported_varaitions[(int32_t)amaster->axis[i].tag] = Vector3i(amaster->axis[i].minimum / 65536, amaster->axis[i].maximum / 65536, amaster->axis[i].def / 65536);
				}
				FT_Done_MM_Var(ft_library, amaster);
			}
			p_font_data->face_init = true;
		}
		
		if (fd->face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS) {
			FT_MM_Var *amaster;
			FT_Get_MM_Var(fd->face, &amaster);
			Vector<hb_variation_t> hb_vars;
			Vector<FT_Fixed> coords;
			coords.resize(amaster->num_axis);
			FT_Get_Var_Design_Coordinates(fd->face, coords.size(), coords.ptrw());
			for (FT_UInt i = 0; i < amaster->num_axis; i++) {
				hb_variation_t var;