### 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 
for (int i = 0; i < custom_effects.size(); i++) {
		Ref<RichTextEffect> effect = custom_effects[i];
		if (!effect.is_valid()) {
			continue;
		}
		if (effect->get_bbcode() == p_bbcode_identifier) {
			return effect;
		}
	}
	return Ref<RichTextEffect>();
}
Dictionary RichTextLabel::parse_expressions_for_values(Vector<String> p_expressions) {