### 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)

bool skip = (trim_chars && l.char_offset + glyphs[i].end > visible_characters) || (trim_glyphs_ltr && (r_processed_glyphs >= visible_glyphs)) || (trim_glyphs_rtl && (r_processed_glyphs < total_glyphs - visible_glyphs));
				if (txt_visible) {
					if (!skip) {
						if (frid != RID()) {
							TS->font_draw_glyph(frid, ci, glyphs[i].font_size, p_ofs + fx_offset + off, gl, font_color);
						} else if ((glyphs[i].flags & TextServer::GRAPHEME_IS_VIRTUAL) != TextServer::GRAPHEME_IS_VIRTUAL) {
							TS->draw_hex_code_box(ci, glyphs[i].font_size, p_ofs + fx_offset + off, gl, font_color);
						}
					}
					r_processed_glyphs++;
				}
				if (skip) {
					
					if (ul_started) {
						ul_started = false;
						float y_off = TS->shaped_text_get_underline_position(rid);
						float underline_width = TS->shaped_text_get_underline_thickness(rid) * theme_cache.base_scale;
						draw_line(ul_start + Vector2(0, y_off), p_ofs + Vector2(off.x, off.y + y_off), ul_color, underline_width);
					}
					if (dot_ul_started) {
						dot_ul_started = false;
						float y_off = TS->shaped_text_get_underline_position(rid);
						float underline_width = TS->shaped_text_get_underline_thickness(rid) * theme_cache.base_scale;
						draw_dashed_line(dot_ul_start + Vector2(0, y_off), p_ofs + Vector2(off.x, off.y + y_off), dot_ul_color, underline_width, underline_width * 2);
					}
					if (st_started) {
						st_started = false;
						float y_off = -TS->shaped_text_get_ascent(rid) + TS->shaped_text_get_size(rid).y / 2;
						float underline_width = TS->shaped_text_get_underline_thickness(rid) * theme_cache.base_scale;
						draw_line(st_start + Vector2(0, y_off), p_ofs + Vector2(off.x, off.y + y_off), st_color, underline_width);