### 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)

sd->objects[p_key].rect.size = p_size;
	sd->objects[p_key].inline_align = p_inline_align;
	sd->objects[p_key].baseline = p_baseline;
	if (sd->valid) {
		
		sd->ascent = 0;
		sd->descent = 0;
		sd->width = 0;
		sd->upos = 0;
		sd->uthk = 0;
		int sd_size = sd->glyphs.size();
		for (int i = 0; i < sd_size; i++) {
			Glyph gl = sd->glyphs[i];
			Variant key;
			if (gl.count == 1) {
				for (const KeyValue<Variant, ShapedTextDataAdvanced::EmbeddedObject> &E : sd->objects) {
					if (E.value.pos == gl.start) {
						key = E.key;
						
					}
				}
			}
			if (key != Variant()) {
				if (sd->orientation == ORIENTATION_HORIZONTAL) {
					sd->objects[key].rect.position.x = sd->width;
					sd->width += sd->objects[key].rect.size.x;
					sd->glyphs.write[i].advance = sd->objects[key].rect.size.x;
				} else {
					sd->objects[key].rect.position.y = sd->width;
					sd->width += sd->objects[key].rect.size.y;