### 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)

int64_t interface_features = FEATURE_SIMPLE_LAYOUT | FEATURE_BIDI_LAYOUT | FEATURE_VERTICAL_LAYOUT | FEATURE_SHAPING | FEATURE_KASHIDA_JUSTIFICATION | FEATURE_BREAK_ITERATORS | FEATURE_FONT_BITMAP | FEATURE_FONT_VARIABLE | FEATURE_CONTEXT_SENSITIVE_CASE_CONVERSION | FEATURE_USE_SUPPORT_DATA;
#ifdef MODULE_FREETYPE_ENABLED
	interface_features |= FEATURE_FONT_DYNAMIC;
#endif
#ifdef MODULE_MSDFGEN_ENABLED
	interface_features |= FEATURE_FONT_MSDF;
#endif
	return interface_features;
}
void TextServerAdvanced::_free_rid(const RID &p_rid) {
	_THREAD_SAFE_METHOD_
	if (font_owner.owns(p_rid)) {
		FontAdvanced *fd = font_owner.get_or_null(p_rid);
		{
			MutexLock lock(fd->mutex);
			font_owner.free(p_rid);
		}
		memdelete(fd);
	} else if (shaped_owner.owns(p_rid)) {
		ShapedTextDataAdvanced *sd = shaped_owner.get_or_null(p_rid);
		{
			MutexLock lock(sd->mutex);
			shaped_owner.free(p_rid);
		}
		memdelete(sd);
	}
}
bool TextServerAdvanced::_has(const RID &p_rid) {