### 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)

}
								draw_rect(Rect2(p_ofs + rect.position + off + coff - frame->padding.position, Size2(table->columns[col].width + h_separation + frame->padding.position.x + frame->padding.size.x, table->rows[row])), (frame->border != Color(0, 0, 0, 0) ? frame->border : border), false);
							}
							for (int j = 0; j < (int)frame->lines.size(); j++) {
								_draw_line(frame, j, p_ofs + rect.position + off + Vector2(0, frame->lines[j].offset.y), rect.size.x, p_base_color, p_outline_size, p_outline_color, p_font_shadow_color, p_shadow_outline_size, p_shadow_ofs, r_processed_glyphs);
							}
							idx++;
						}
					} break;
					default:
						break;
				}
			}
		}
		const Glyph *glyphs = TS->shaped_text_get_glyphs(rid);
		int gl_size = TS->shaped_text_get_glyph_count(rid);
		Vector2 gloff = off;
		
		int processed_glyphs_ol = r_processed_glyphs;
		for (int i = 0; i < gl_size; i++) {
			Item *it = _get_item_at_pos(it_from, it_to, glyphs[i].start);
			int size = _find_outline_size(it, p_outline_size);
			Color font_color = _find_color(it, p_base_color);
			Color font_outline_color = _find_outline_color(it, p_outline_color);
			Color font_shadow_color = p_font_shadow_color;
			if ((size <= 0 || font_outline_color.a == 0) && (font_shadow_color.a == 0)) {
				gloff.x += glyphs[i].advance;
				continue;
			}