### 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)

}
		icu_data_loaded = true;
	}
#endif
	return true;
}
String TextServerAdvanced::_get_support_data_filename() const {
	return _MKSTR(ICU_DATA_NAME);
}
String TextServerAdvanced::_get_support_data_info() const {
	return String("ICU break iteration data (") + _MKSTR(ICU_DATA_NAME) + String(").");
}
bool TextServerAdvanced::_save_support_data(const String &p_filename) const {
	_THREAD_SAFE_METHOD_
#ifdef ICU_STATIC_DATA
	
	Ref<FileAccess> f = FileAccess::open(p_filename, FileAccess::WRITE);
	if (f.is_null()) {
		return false;
	}
	PackedByteArray icu_data;
	icu_data.resize(U_ICUDATA_SIZE);
	memcpy(icu_data.ptrw(), U_ICUDATA_ENTRY_POINT, U_ICUDATA_SIZE);
	f->store_buffer(icu_data);
	return true;
#else
	return false;
#endif
}
bool TextServerAdvanced::_is_locale_right_to_left(const String &p_locale) const {