### 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)

set_physics_process_internal(false); 
			} else {
				
				if ((progress_delay > 0) && (OS::get_singleton()->get_ticks_msec() - loading_started >= (uint64_t)progress_delay)) {
					Vector2 p_size = Vector2(size.width - (theme_cache.normal_style->get_offset().x + vscroll->get_combined_minimum_size().width) * 2, vscroll->get_combined_minimum_size().width);
					Vector2 p_pos = Vector2(theme_cache.normal_style->get_offset().x, size.height - theme_cache.normal_style->get_offset().y - vscroll->get_combined_minimum_size().width);
					draw_style_box(theme_cache.progress_bg_style, Rect2(p_pos, p_size));
					bool right_to_left = is_layout_rtl();
					double r = loaded.load();
					int mp = theme_cache.progress_fg_style->get_minimum_size().width;
					int p = round(r * (p_size.width - mp));
					if (right_to_left) {
						int p_remaining = round((1.0 - r) * (p_size.width - mp));
						draw_style_box(theme_cache.progress_fg_style, Rect2(p_pos + Point2(p_remaining, 0), Size2(p + theme_cache.progress_fg_style->get_minimum_size().width, p_size.height)));
					} else {
						draw_style_box(theme_cache.progress_fg_style, Rect2(p_pos, Size2(p + theme_cache.progress_fg_style->get_minimum_size().width, p_size.height)));
					}
				}
			}
			
			Rect2 text_rect = _get_text_rect();
			float vofs = vscroll->get_value();
			
			int to_line = main->first_invalid_line.load();
			int from_line = _find_first_line(0, to_line, vofs);
			Point2 shadow_ofs(theme_cache.shadow_offset_x, theme_cache.shadow_offset_y);
			visible_paragraph_count = 0;
			visible_line_count = 0;
			
			Point2 ofs = text_rect.get_position() + Vector2(0, main->lines[from_line].offset.y - vofs);