### 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)

String l = p_locale.get_slicec('_', 0);
	if ((l == "ar") || (l == "dv") || (l == "he") || (l == "fa") || (l == "ff") || (l == "ku") || (l == "ur")) {
		return true;
	} else {
		return false;
	}
}
_FORCE_INLINE_ void TextServerAdvanced::_insert_feature(const  &p_name, int32_t p_tag, Variant::Type p_vtype, bool p_hidden) {
	FeatureInfo fi;
	fi.name = p_name;
	fi.vtype = p_vtype;
	fi.hidden = p_hidden;
	feature_sets.insert(p_name, p_tag);
	feature_sets_inv.insert(p_tag, fi);
}
void TextServerAdvanced::_insert_feature_sets() {
	
	
	_insert_feature("access_all_alternates", HB_TAG('a', 'a', 'l', 't'), Variant::Type::INT, false);
	_insert_feature("above_base_forms", HB_TAG('a', 'b', 'v', 'f'), Variant::Type::INT, true);
	_insert_feature("above_base_mark_positioning", HB_TAG('a', 'b', 'v', 'm'), Variant::Type::INT, true);
	_insert_feature("above_base_substitutions", HB_TAG('a', 'b', 'v', 's'), Variant::Type::INT, true);
	_insert_feature("alternative_fractions", HB_TAG('a', 'f', 'r', 'c'), Variant::Type::INT, false);
	_insert_feature("akhands", HB_TAG('a', 'k', 'h', 'n'), Variant::Type::INT, true);
	_insert_feature("below_base_forms", HB_TAG('b', 'l', 'w', 'f'), Variant::Type::INT, true);
	_insert_feature("below_base_mark_positioning", HB_TAG('b', 'l', 'w', 'm'), Variant::Type::INT, true);
	_insert_feature("below_base_substitutions", HB_TAG('b', 'l', 'w', 's'), Variant::Type::INT, true);