### 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)

TextDirection get_text_direction() const;
	void set_language(const String &p_language);
	String get_language() const;
	void set_autowrap_mode(TextServer::AutowrapMode p_mode);
	TextServer::AutowrapMode get_autowrap_mode() const;
	void set_structured_text_bidi_override(TextServer::StructuredTextParser p_parser);
	TextServer::StructuredTextParser get_structured_text_bidi_override() const;
	void set_structured_text_bidi_override_options(Array p_args);
	Array get_structured_text_bidi_override_options() const;
	void set_visible_characters(int p_visible);
	int get_visible_characters() const;
	int get_character_line(int p_char);
	int get_character_paragraph(int p_char);
	int get_total_character_count() const;
	int get_total_glyph_count() const;
	void set_visible_ratio(float p_ratio);
	float get_visible_ratio() const;
	TextServer::VisibleCharactersBehavior get_visible_characters_behavior() const;
	void set_visible_characters_behavior(TextServer::VisibleCharactersBehavior p_behavior);
	void set_effects(Array p_effects);
	Array get_effects();
	void install_effect(const Variant effect);
	virtual Size2 get_minimum_size() const override;
	RichTextLabel(const String &p_text = String());
	~RichTextLabel();
};
VARIANT_ENUM_CAST(RichTextLabel::ListType);
VARIANT_ENUM_CAST(RichTextLabel::ItemType);
#endif