### 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)

const  lang = (p_language.is_empty()) ? TranslationServer::get_singleton()->get_tool_locale() : p_language;
	String res = p_string;
	for (int i = 0; i < num_systems.size(); i++) {
		if (num_systems[i].lang.has(lang)) {
			if (num_systems[i].digits.is_empty()) {
				return p_string;
			}
			res.replace(num_systems[i].exp, "e");
			char32_t *data = res.ptrw();
			for (int j = 0; j < res.length(); j++) {
				if (data[j] == num_systems[i].digits[10]) {
					data[j] = '.';
				} else {
					for (int k = 0; k < 10; k++) {
						if (data[j] == num_systems[i].digits[k]) {
							data[j] = 0x30 + k;
						}
					}
				}
			}
			
		}
	}
	return res;
}
String TextServerAdvanced::_percent_sign(const String &p_language) const {