### 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)

};
	struct ItemFX : public Item {
		double elapsed_time = 0.f;
		bool connected = true;
	};
	struct ItemShake : public ItemFX {
		int strength = 0;
		float rate = 0.0f;
		uint64_t _current_rng = 0;
		uint64_t _previous_rng = 0;
		Vector2 prev_off;
		ItemShake() { type = ITEM_SHAKE; }
		void reroll_random() {
			_previous_rng = _current_rng;
			_current_rng = Math::rand();
		}
		uint64_t offset_random(int p_index) {
			return (_current_rng >> (p_index % 64)) |
					(_current_rng << (64 - (p_index % 64)));
		}
		uint64_t offset_previous_random(int p_index) {
			return (_previous_rng >> (p_index % 64)) |
					(_previous_rng << (64 - (p_index % 64)));
		}
	};
	struct ItemWave : public ItemFX {
		float frequency = 1.0f;
		float amplitude = 1.0f;
		Vector2 prev_off;
		ItemWave() { type = ITEM_WAVE; }