### 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)

gl.font_rid = sd_glyphs[i].font_rid;
					gl.font_size = sd_glyphs[i].font_size;
					gl.flags = GRAPHEME_IS_BREAK_SOFT | GRAPHEME_IS_VIRTUAL | GRAPHEME_IS_SPACE;
					if (sd_glyphs[i].flags & GRAPHEME_IS_RTL) {
						gl.flags |= GRAPHEME_IS_RTL;
						for (int j = sd_glyphs[i].count - 1; j >= 0; j--) {
							sd_glyphs_new[sd_shift + i + j + 1] = sd_glyphs_new[sd_shift + i + j];
						}
						sd_glyphs_new[sd_shift + i] = gl;
					} else {
						sd_glyphs_new[sd_shift + i + count] = gl;
					}
					sd_shift++;
					ERR_FAIL_COND_V_MSG(sd_shift > sd->break_inserts, false, "Invalid break insert count!");
				}
			}
			i += (sd_glyphs[i].count - 1);
		}
	}
	if (sd_shift < sd->break_inserts) {
		
		glyphs_new.resize(sd->glyphs.size() + sd_shift);
	}
	if (sd->break_inserts > 0) {
		sd->glyphs = glyphs_new;
	}
	sd->line_breaks_valid = true;
	return sd->line_breaks_valid;
}
_FORCE_INLINE_ int64_t _generate_kashida_justification_opportunies(const String &p_data, int64_t p_start, int64_t p_end) {