### 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)

case FONT_LCD_SUBPIXEL_LAYOUT_VBGR: {
						aa_mode = FT_RENDER_MODE_LCD_V;
						bgra = true;
					} 
					default: {
						aa_mode = FT_RENDER_MODE_NORMAL;
					} 
				}
			} 
		}
		if (!outline) {
			if (!p_font_data->msdf) {
				error = FT_Render_Glyph(fd->face->glyph, aa_mode);
			}
			FT_GlyphSlot slot = fd->face->glyph;
			if (!error) {
				if (p_font_data->msdf) {
#ifdef MODULE_MSDFGEN_ENABLED
					gl = rasterize_msdf(p_font_data, fd, p_font_data->msdf_range, rect_range, &slot->outline, Vector2((h + (1 << 9)) >> 10, (v + (1 << 9)) >> 10) / 64.0);
#else
					fd->glyph_map[p_glyph] = FontGlyph();
					ERR_FAIL_V_MSG(false, "Compiled without MSDFGEN support!");
#endif
				} else {
					gl = rasterize_bitmap(fd, rect_range, slot->bitmap, slot->bitmap_top, slot->bitmap_left, Vector2((h + (1 << 9)) >> 10, (v + (1 << 9)) >> 10) / 64.0, bgra);
				}
			}
		} else {
			FT_Stroker stroker;
			if (FT_Stroker_New(ft_library, &stroker) != 0) {