### 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();
	int line_count = 0;
	int to_line = main->first_invalid_line.load();
	for (int i = 0; i < to_line; i++) {
		MutexLock lock(main->lines[i].text_buf->get_mutex());
		if ((line_count <= p_line) && (p_line <= line_count + main->lines[i].text_buf->get_line_count())) {
			float line_offset = 0.f;
			for (int j = 0; j < p_line - line_count; j++) {
				line_offset += main->lines[i].text_buf->get_line_size(j).y + theme_cache.line_separation;
			}
			return main->lines[i].offset.y + line_offset;
		}
		line_count += main->lines[i].text_buf->get_line_count();
	}
	return 0;
}
float RichTextLabel::get_paragraph_offset(int p_paragraph) {