### 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)

last_cluster_valid = last_cluster_valid && ((glyph_info[i].codepoint != 0) || (p_sd->text[glyph_info[i].cluster] == 0x0009) || (u_isblank(p_sd->text[glyph_info[i].cluster]) && (gl.advance != 0)) || (!u_isblank(p_sd->text[glyph_info[i].cluster]) && !u_isgraph(p_sd->text[glyph_info[i].cluster])));
			}
		}
		if (p_direction == HB_DIRECTION_LTR || p_direction == HB_DIRECTION_TTB) {
			for (unsigned int j = last_cluster_index; j < glyph_count; j++) {
				w[j].end = p_end;
			}
		}
		w[last_cluster_index].count = glyph_count - last_cluster_index;
		if (p_direction == HB_DIRECTION_RTL || p_direction == HB_DIRECTION_BTT) {
			w[last_cluster_index].flags |= GRAPHEME_IS_RTL;
		}
		if (last_cluster_valid) {
			w[last_cluster_index].flags |= GRAPHEME_IS_VALID;
		}
		
		int failed_subrun_start = p_end + 1;
		int failed_subrun_end = p_start;
		for (unsigned int i = 0; i < glyph_count; i++) {
			if ((w[i].flags & GRAPHEME_IS_VALID) == GRAPHEME_IS_VALID) {
				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);
					failed_subrun_start = p_end + 1;
					failed_subrun_end = p_start;
				}
				for (int j = 0; j < w[i].count; j++) {
					if (p_sd->orientation == ORIENTATION_HORIZONTAL) {
						p_sd->ascent = MAX(p_sd->ascent, -w[i + j].y_off);
						p_sd->descent = MAX(p_sd->descent, w[i + j].y_off);
					} else {