### 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 
if (expr.size() < 1) {
				add_text("[");
				pos = brk_pos + 1;
			} else {
				String identifier = expr[0];
				expr.remove_at(0);
				Dictionary properties = parse_expressions_for_values(expr);
				Ref<RichTextEffect> effect = _get_custom_effect_by_code(identifier);
				if (!effect.is_null()) {
					push_customfx(effect, properties);
					pos = brk_end + 1;
					tag_stack.push_front(identifier);
				} else {
					add_text("["); 
					pos = brk_pos + 1;
				}
			}
		}
	}
	Vector<ItemFX *> fx_items;
	for (Item *E : main->subitems) {
		Item *subitem = static_cast<Item *>(E);
		_fetch_item_fx_stack(subitem, fx_items);
		if (fx_items.size()) {
			set_process_internal(true);
			break;
		}
	}
}
void RichTextLabel::scroll_to_selection() {