### 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("get_parsed_text"), &RichTextLabel::get_parsed_text);
	ClassDB::bind_method(D_METHOD("add_text", "text"), &RichTextLabel::add_text);
	ClassDB::bind_method(D_METHOD("set_text", "text"), &RichTextLabel::set_text);
	ClassDB::bind_method(D_METHOD("add_image", "image", "width", "height", "color", "inline_align", "region"), &RichTextLabel::add_image, DEFVAL(0), DEFVAL(0), DEFVAL(Color(1.0, 1.0, 1.0)), DEFVAL(INLINE_ALIGNMENT_CENTER), DEFVAL(Rect2(0, 0, 0, 0)));
	ClassDB::bind_method(D_METHOD("newline"), &RichTextLabel::add_newline);
	ClassDB::bind_method(D_METHOD("remove_paragraph", "paragraph"), &RichTextLabel::remove_paragraph);
	ClassDB::bind_method(D_METHOD("push_font", "font", "font_size"), &RichTextLabel::push_font);
	ClassDB::bind_method(D_METHOD("push_font_size", "font_size"), &RichTextLabel::push_font_size);
	ClassDB::bind_method(D_METHOD("push_normal"), &RichTextLabel::push_normal);
	ClassDB::bind_method(D_METHOD("push_bold"), &RichTextLabel::push_bold);
	ClassDB::bind_method(D_METHOD("push_bold_italics"), &RichTextLabel::push_bold_italics);
	ClassDB::bind_method(D_METHOD("push_italics"), &RichTextLabel::push_italics);
	ClassDB::bind_method(D_METHOD("push_mono"), &RichTextLabel::push_mono);
	ClassDB::bind_method(D_METHOD("push_color", "color"), &RichTextLabel::push_color);
	ClassDB::bind_method(D_METHOD("push_outline_size", "outline_size"), &RichTextLabel::push_outline_size);
	ClassDB::bind_method(D_METHOD("push_outline_color", "color"), &RichTextLabel::push_outline_color);
	ClassDB::bind_method(D_METHOD("push_paragraph", "alignment", "base_direction", "language", "st_parser"), &RichTextLabel::push_paragraph, DEFVAL(TextServer::DIRECTION_AUTO), DEFVAL(""), DEFVAL(TextServer::STRUCTURED_TEXT_DEFAULT));
	ClassDB::bind_method(D_METHOD("push_indent", "level"), &RichTextLabel::push_indent);
	ClassDB::bind_method(D_METHOD("push_list", "level", "type", "capitalize"), &RichTextLabel::push_list);
	ClassDB::bind_method(D_METHOD("push_meta", "data"), &RichTextLabel::push_meta);
	ClassDB::bind_method(D_METHOD("push_hint", "description"), &RichTextLabel::push_hint);
	ClassDB::bind_method(D_METHOD("push_underline"), &RichTextLabel::push_underline);
	ClassDB::bind_method(D_METHOD("push_strikethrough"), &RichTextLabel::push_strikethrough);
	ClassDB::bind_method(D_METHOD("push_table", "columns", "inline_align", "align_to_row"), &RichTextLabel::push_table, DEFVAL(INLINE_ALIGNMENT_TOP), DEFVAL(-1));
	ClassDB::bind_method(D_METHOD("push_dropcap", "string", "font", "size", "dropcap_margins", "color", "outline_size", "outline_color"), &RichTextLabel::push_dropcap, DEFVAL(Rect2()), DEFVAL(Color(1, 1, 1)), DEFVAL(0), DEFVAL(Color(0, 0, 0, 0)));
	ClassDB::bind_method(D_METHOD("set_table_column_expand", "column", "expand", "ratio"), &RichTextLabel::set_table_column_expand);
	ClassDB::bind_method(D_METHOD("set_cell_row_background_color", "odd_row_bg", "even_row_bg"), &RichTextLabel::set_cell_row_background_color);
	ClassDB::bind_method(D_METHOD("set_cell_border_color", "color"), &RichTextLabel::set_cell_border_color);