### 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)

int32_t prop = u_gep_pchr, UCHAR_JOINING_TYPE);
	return (prop != U_JT_RIGHT_JOINING) && (prop != U_JT_NON_JOINING) ? !is_ligature(p_pchr, p_chr) : false;
}
bool TextServerAdvanced::_has_feature(Feature p_feature) const {
	switch (p_feature) {
		case FEATURE_SIMPLE_LAYOUT:
		case FEATURE_BIDI_LAYOUT:
		case FEATURE_VERTICAL_LAYOUT:
		case FEATURE_SHAPING:
		case FEATURE_KASHIDA_JUSTIFICATION:
		case FEATURE_BREAK_ITERATORS:
		case FEATURE_FONT_BITMAP:
#ifdef MODULE_FREETYPE_ENABLED
		case FEATURE_FONT_DYNAMIC:
#endif
#ifdef MODULE_MSDFGEN_ENABLED
		case FEATURE_FONT_MSDF:
#endif
		case FEATURE_FONT_VARIABLE:
		case FEATURE_CONTEXT_SENSITIVE_CASE_CONVERSION:
		case FEATURE_USE_SUPPORT_DATA:
		case FEATURE_UNICODE_IDENTIFIERS:
		case FEATURE_UNICODE_SECURITY:
			return true;
		default: {
		}
	}
	return false;
}
String TextServerAdvanced::_get_name() const {