### 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)

Dictionary d;
	for (int i = 0; i < p_expressions.size(); i++) {
		String expression = p_expressions[i];
		Array a;
		Vector<String> parts = expression.split("=", true);
		String key = parts[0];
		if (parts.size() != 2) {
			return d;
		}
		Vector<String> values = parts[1].split(",", false);
#ifdef MODULE_REGEX_ENABLED
		RegEx color = RegEx();
		color.compile("^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$");
		RegEx nodepath = RegEx();
		nodepath.compile("^\\$");
		RegEx boolean = RegEx();
		boolean.compile("^(true|false)$");
		RegEx decimal = RegEx();
		decimal.compile("^-?^.?\\d+(\\.\\d+?)?$");
		RegEx numerical = RegEx();
		numerical.compile("^\\d+$");
		for (int j = 0; j < values.size(); j++) {
			if (!color.search(values[j]).is_null()) {