### 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 
_validate_line_caches();
	if (p_paragraph <= 0) {
		vscroll->set_value(0);
	} else if (p_paragraph >= main->first_invalid_line.load()) {
		vscroll->set_value(vscroll->get_max());
	} else {
		vscroll->set_value(main->lines[p_paragraph].offset.y);
	}
}
int RichTextLabel::get_paragraph_count() const {
	return current_frame->lines.size();
}
int RichTextLabel::get_visible_paragraph_count() const {