### 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 *sizeitem = p_item;
	while (sizeitem) {
		if (sizeitem->type == ITEM_FONT_SIZE) {
			ItemFontSize *fi = static_cast<ItemFontSize *>(sizeitem);
			return fi;
		}
		sizeitem = sizeitem->parent;
	}
	return nullptr;
}
int RichTextLabel::_find_outline_size(Item *p_item, int p_default) {
	Item *sizeitem = p_item;
	while (sizeitem) {
		if (sizeitem->type == ITEM_OUTLINE_SIZE) {
			ItemOutlineSize *fi = static_cast<ItemOutlineSize *>(sizeitem);
			return fi->outline_size;
		}
		sizeitem = sizeitem->parent;
	}
	return p_default;
}
RichTextLabel::ItemDropcap *RichTextLabel::_find_dc_item(Item *p_item) {