### 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)

double gla = Math::round(_font_get_glyph_advance(f, fs, w[i + j].index).x * 0.5);
						p_sd->ascent = MAX(p_sd->ascent, gla);
						p_sd->descent = MAX(p_sd->descent, gla);
					}
					p_sd->width += w[i + j].advance;
					w[i + j].start += p_sd->start;
					w[i + j].end += p_sd->start;
					p_sd->glyphs.push_back(w[i + j]);
				}
			} else {
				if (failed_subrun_start >= w[i].start) {
					failed_subrun_start = w[i].start;
				}
				if (failed_subrun_end <= w[i].end) {
					failed_subrun_end = w[i].end;
				}
			}
			i += w[i].count - 1;
		}
		memfree(w);
		if (failed_subrun_start != p_end + 1) {
			_shape_run(p_sd, failed_subrun_start, failed_subrun_end, p_script, p_direction, p_fonts, p_span, p_fb_index + 1, p_start, p_end);
		}
		p_sd->ascent = MAX(p_sd->ascent, _font_get_ascent(f, fs));
		p_sd->descent = MAX(p_sd->descent, _font_get_descent(f, fs));
		p_sd->upos = MAX(p_sd->upos, _font_get_underline_position(f, fs));
		p_sd->uthk = MAX(p_sd->uthk, _font_get_underline_thickness(f, fs));
	}
}
bool TextServerAdvanced::_shaped_text_shape(const RID &p_shaped) {