### 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)

}
	}
	if ((elongation_count > 0) && p_jst_flags.has_flag(JUSTIFICATION_KASHIDA)) {
		double delta_width_per_kashida = (p_width - justification_width) / elongation_count;
		for (int i = start_pos; i <= end_pos; i++) {
			Glyph &gl = sd->glyphs.write[i];
			if (gl.count > 0) {
				if (((gl.flags & GRAPHEME_IS_ELONGATION) == GRAPHEME_IS_ELONGATION) && (gl.advance > 0)) {
					if ((i > 0) && ((sd->glyphs[i - 1].flags & GRAPHEME_IS_ELONGATION) != GRAPHEME_IS_ELONGATION)) {
						
						int count = delta_width_per_kashida / gl.advance;
						int prev_count = gl.repeat;
						if ((gl.flags & GRAPHEME_IS_VIRTUAL) == GRAPHEME_IS_VIRTUAL) {
							gl.repeat = MAX(count, 0);
						} else {
							gl.repeat = MAX(count + 1, 1);
						}
						justification_width += (gl.repeat - prev_count) * gl.advance;
					}
				}
			}
		}
	}
	if ((space_count > 0) && p_jst_flags.has_flag(JUSTIFICATION_WORD_BOUND)) {
		double delta_width_per_space = (p_width - justification_width) / space_count;
		double adv_remain = 0;
		for (int i = start_pos; i <= end_pos; i++) {
			Glyph &gl = sd->glyphs.write[i];
			if (gl.count > 0) {
				if ((gl.flags & GRAPHEME_IS_SPACE) == GRAPHEME_IS_SPACE) {