### 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)

ShapedTextDataAdvanced *parent = shaped_owner.get_or_null(p_shaped->parent);
	for (const KeyValue<Variant, ShapedTextDataAdvanced::EmbeddedObject> &E : parent->objects) {
		if (E.value.pos >= p_shaped->start && E.value.pos < p_shaped->end) {
			p_shaped->objects[E.key] = E.value;
		}
	}
	for (int i = 0; i < parent->spans.size(); i++) {
		ShapedTextDataAdvanced::Span span = parent->spans[i];
		if (span.start >= p_shaped->end || span.end <= p_shaped->start) {
			continue;
		}
		span.start = MAX(p_shaped->start, span.start);
		span.end = MIN(p_shaped->end, span.end);
		p_shaped->spans.push_back(span);
	}
	p_shaped->parent = RID();
}
RID TextServerAdvanced::_create_shaped_text(TextServer::Direction p_direction, TextServer::Orientation p_orientation) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_V_MSG(p_direction == DIRECTION_INHERITED, RID(), "Invalid text direction.");
	ShapedTextDataAdvanced *sd = memnew(ShapedTextDataAdvanced);
	sd->hb_buffer = hb_buffer_create();
	sd->direction = p_direction;
	sd->orientation = p_orientation;
	return shaped_owner.make_rid(sd);
}
void TextServerAdvanced::_shaped_text_clear(const RID &p_shaped) {