### 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_visible_ratio"), &RichTextLabel::get_visible_ratio);
	ClassDB::bind_method(D_METHOD("get_character_line", "character"), &RichTextLabel::get_character_line);
	ClassDB::bind_method(D_METHOD("get_character_paragraph", "character"), &RichTextLabel::get_character_paragraph);
	ClassDB::bind_method(D_METHOD("get_total_character_count"), &RichTextLabel::get_total_character_count);
	ClassDB::bind_method(D_METHOD("set_use_bbcode", "enable"), &RichTextLabel::set_use_bbcode);
	ClassDB::bind_method(D_METHOD("is_using_bbcode"), &RichTextLabel::is_using_bbcode);
	ClassDB::bind_method(D_METHOD("get_line_count"), &RichTextLabel::get_line_count);
	ClassDB::bind_method(D_METHOD("get_visible_line_count"), &RichTextLabel::get_visible_line_count);
	ClassDB::bind_method(D_METHOD("get_paragraph_count"), &RichTextLabel::get_paragraph_count);
	ClassDB::bind_method(D_METHOD("get_visible_paragraph_count"), &RichTextLabel::get_visible_paragraph_count);
	ClassDB::bind_method(D_METHOD("get_content_height"), &RichTextLabel::get_content_height);
	ClassDB::bind_method(D_METHOD("get_content_width"), &RichTextLabel::get_content_width);
	ClassDB::bind_method(D_METHOD("get_line_offset", "line"), &RichTextLabel::get_line_offset);
	ClassDB::bind_method(D_METHOD("get_paragraph_offset", "paragraph"), &RichTextLabel::get_paragraph_offset);
	ClassDB::bind_method(D_METHOD("parse_expressions_for_values", "expressions"), &RichTextLabel::parse_expressions_for_values);
	ClassDB::bind_method(D_METHOD("set_effects", "effects"), &RichTextLabel::set_effects);
	ClassDB::bind_method(D_METHOD("get_effects"), &RichTextLabel::get_effects);
	ClassDB::bind_method(D_METHOD("install_effect", "effect"), &RichTextLabel::install_effect);
	ClassDB::bind_method(D_METHOD("get_menu"), &RichTextLabel::get_menu);
	ClassDB::bind_method(D_METHOD("is_menu_visible"), &RichTextLabel::is_menu_visible);
	
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "bbcode_enabled"), "set_use_bbcode", "is_using_bbcode");
	ADD_PROPERTY(PropertyInfo(Variant::STRING, "text", PROPERTY_HINT_MULTILINE_TEXT), "set_text", "get_text");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "fit_content"), "set_fit_content", "is_fit_content_enabled");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "scroll_active"), "set_scroll_active", "is_scroll_active");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "scroll_following"), "set_scroll_follow", "is_scroll_following");
	ADD_PROPERTY(PropertyInfo(Variant::INT, "autowrap_mode", PROPERTY_HINT_ENUM, "Off,Arbitrary,Word,Word (Smart)"), "set_autowrap_mode", "get_autowrap_mode");
	ADD_PROPERTY(PropertyInfo(Variant::INT, "tab_size", PROPERTY_HINT_RANGE, "0,24,1"), "set_tab_size", "get_tab_size");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "context_menu_enabled"), "set_context_menu_enabled", "is_context_menu_enabled");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "shortcut_keys_enabled"), "set_shortcut_keys_enabled", "is_shortcut_keys_enabled");