### 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)

ClassDB::bind_method(D_METHOD("set_cell_size_override", "min_size", "max_size"), &RichTextLabel::set_cell_size_override);
	ClassDB::bind_method(D_METHOD("set_cell_padding", "padding"), &RichTextLabel::set_cell_padding);
	ClassDB::bind_method(D_METHOD("push_cell"), &RichTextLabel::push_cell);
	ClassDB::bind_method(D_METHOD("push_fgcolor", "fgcolor"), &RichTextLabel::push_fgcolor);
	ClassDB::bind_method(D_METHOD("push_bgcolor", "bgcolor"), &RichTextLabel::push_bgcolor);
	ClassDB::bind_method(D_METHOD("push_customfx", "effect", "env"), &RichTextLabel::push_customfx);
	ClassDB::bind_method(D_METHOD("pop"), &RichTextLabel::pop);
	ClassDB::bind_method(D_METHOD("clear"), &RichTextLabel::clear);
	ClassDB::bind_method(D_METHOD("set_structured_text_bidi_override", "parser"), &RichTextLabel::set_structured_text_bidi_override);
	ClassDB::bind_method(D_METHOD("get_structured_text_bidi_override"), &RichTextLabel::get_structured_text_bidi_override);
	ClassDB::bind_method(D_METHOD("set_structured_text_bidi_override_options", "args"), &RichTextLabel::set_structured_text_bidi_override_options);
	ClassDB::bind_method(D_METHOD("get_structured_text_bidi_override_options"), &RichTextLabel::get_structured_text_bidi_override_options);
	ClassDB::bind_method(D_METHOD("set_text_direction", "direction"), &RichTextLabel::set_text_direction);
	ClassDB::bind_method(D_METHOD("get_text_direction"), &RichTextLabel::get_text_direction);
	ClassDB::bind_method(D_METHOD("set_language", "language"), &RichTextLabel::set_language);
	ClassDB::bind_method(D_METHOD("get_language"), &RichTextLabel::get_language);
	ClassDB::bind_method(D_METHOD("set_autowrap_mode", "autowrap_mode"), &RichTextLabel::set_autowrap_mode);
	ClassDB::bind_method(D_METHOD("get_autowrap_mode"), &RichTextLabel::get_autowrap_mode);
	ClassDB::bind_method(D_METHOD("set_meta_underline", "enable"), &RichTextLabel::set_meta_underline);
	ClassDB::bind_method(D_METHOD("is_meta_underlined"), &RichTextLabel::is_meta_underlined);
	ClassDB::bind_method(D_METHOD("set_hint_underline", "enable"), &RichTextLabel::set_hint_underline);
	ClassDB::bind_method(D_METHOD("is_hint_underlined"), &RichTextLabel::is_hint_underlined);
	ClassDB::bind_method(D_METHOD("set_scroll_active", "active"), &RichTextLabel::set_scroll_active);
	ClassDB::bind_method(D_METHOD("is_scroll_active"), &RichTextLabel::is_scroll_active);
	ClassDB::bind_method(D_METHOD("set_scroll_follow", "follow"), &RichTextLabel::set_scroll_follow);
	ClassDB::bind_method(D_METHOD("is_scroll_following"), &RichTextLabel::is_scroll_following);
	ClassDB::bind_method(D_METHOD("get_v_scroll_bar"), &RichTextLabel::get_v_scroll_bar);
	ClassDB::bind_method(D_METHOD("scroll_to_line", "line"), &RichTextLabel::scroll_to_line);
	ClassDB::bind_method(D_METHOD("scroll_to_paragraph", "paragraph"), &RichTextLabel::scroll_to_paragraph);
	ClassDB::bind_method(D_METHOD("scroll_to_selection"), &RichTextLabel::scroll_to_selection);