### 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)

int sd_size = p_sd->glyphs.size();
		const Glyph *sd_glyphs = p_sd->glyphs.ptr();
		for (int ov = 0; ov < p_sd->bidi_override.size(); ov++) {
			UErrorCode err = U_ZERO_ERROR;
			if (p_sd->bidi_override[ov].x >= p_start + p_length || p_sd->bidi_override[ov].y <= p_start) {
				continue;
			}
			int ov_start = _convert_pos_inv(p_sd, p_sd->bidi_override[ov].x);
			int start = MAX(0, _convert_pos_inv(p_sd, p_start) - ov_start);
			int end = MIN(_convert_pos_inv(p_sd, p_start + p_length), _convert_pos_inv(p_sd, p_sd->bidi_override[ov].y)) - ov_start;
			ERR_FAIL_COND_V_MSG((start < 0 || end - start > p_new_sd->utf16.length()), false, "Invalid BiDi override range.");
			
			UBiDi *bidi_iter = ubidi_openSized(end - start, 0, &err);
			ERR_FAIL_COND_V_MSG(U_FAILURE(err), false, u_errorName(err));
			ubidi_setLine(p_sd->bidi_iter[ov], start, end, bidi_iter, &err);
			if (U_FAILURE(err)) {
				ubidi_close(bidi_iter);
				ERR_FAIL_V_MSG(false, u_errorName(err));
			}
			p_new_sd->bidi_iter.push_back(bidi_iter);
			err = U_ZERO_ERROR;
			int bidi_run_count = ubidi_countRuns(bidi_iter, &err);
			ERR_FAIL_COND_V_MSG(U_FAILURE(err), false, u_errorName(err));
			for (int i = 0; i < bidi_run_count; i++) {
				int32_t _bidi_run_start = 0;
				int32_t _bidi_run_length = 0;
				ubidi_getVisualRun(bidi_iter, i, &_bidi_run_start, &_bidi_run_length);
				int32_t bidi_run_start = _convert_pos(p_sd, ov_start + start + _bidi_run_start);
				int32_t bidi_run_end = _convert_pos(p_sd, ov_start + start + _bidi_run_start + _bidi_run_length);
				for (int j = 0; j < sd_size; j++) {