### 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)

switch (sd->orientation) {
				case ORIENTATION_HORIZONTAL: {
					if (is_rtl) {
						bidi_run_direction = HB_DIRECTION_LTR;
					} else {
						bidi_run_direction = HB_DIRECTION_RTL;
					}
				} 
				case ORIENTATION_VERTICAL: {
					if (is_rtl) {
						bidi_run_direction = HB_DIRECTION_TTB;
					} else {
						bidi_run_direction = HB_DIRECTION_BTT;
					}
				}
			}
			int32_t bidi_run_start = _convert_pos(sd, start + _bidi_run_start);
			int32_t bidi_run_end = _convert_pos(sd, start + _bidi_run_start + _bidi_run_length);
			
			int scr_from = (is_rtl) ? 0 : sd->script_iter->script_ranges.size() - 1;
			int scr_to = (is_rtl) ? sd->script_iter->script_ranges.size() : -1;
			int scr_delta = (is_rtl) ? +1 : -1;
			for (int j = scr_from; j != scr_to; j += scr_delta) {
				if ((sd->script_iter->script_ranges[j].start < bidi_run_end) && (sd->script_iter->script_ranges[j].end > bidi_run_start)) {
					int32_t script_run_start = MAX(sd->script_iter->script_ranges[j].start, bidi_run_start);
					int32_t script_run_end = MIN(sd->script_iter->script_ranges[j].end, bidi_run_end);
					char scr_buffer[5] = { 0, 0, 0, 0, 0 };
					hb_tag_to_string(hb_script_to_iso15924_tag(sd->script_iter->script_ranges[j].script), scr_buffer);
					String script_code = String(scr_buffer);
					int spn_from = (is_rtl) ? 0 : sd->spans.size() - 1;