### Godot version

master ([06ccbfe](https://github.com/godotengine/godot/commit/06ccbfe8eec6e840db3df2360dc2804386f940b8))

### System information

PopOS 22.04

### Issue description

Sometimes the doc page is broken when the engine is closed and then restarted.
Closing the doc and opening it again fixes it.

![2023-05-27_22-15](https://github.com/godotengine/godot/assets/3624853/ed202a55-03e8-420a-bc1c-ccfc7f7cd02a)


### Steps to reproduce

- Open a documentation page for any node
- Restart Godot

### Minimal reproduction project

NA

EDIT : Added the commit hash @Calinou 
Item *item = p_item;
	while (item) {
		if (item->type == ITEM_FGCOLOR) {
			ItemFGColor *color = static_cast<ItemFGColor *>(item);
			return color->color;
		}
		item = item->parent;
	}
	return Color(0, 0, 0, 0);
}
bool RichTextLabel::_find_layout_subitem(Item *from, Item *to) {
	if (from && from != to) {
		if (from->type != ITEM_FONT && from->type != ITEM_COLOR && from->type != ITEM_UNDERLINE && from->type != ITEM_STRIKETHROUGH) {
			return true;
		}
		for (Item *E : from->subitems) {
			bool layout = _find_layout_subitem(E, to);
			if (layout) {
				return true;
			}
		}
	}
	return false;
}
void RichTextLabel::_thread_function(void *p_userdata) {