### 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 *item = p_item;
	while (item) {
		if (item->type == ITEM_COLOR) {
			ItemColor *color = static_cast<ItemColor *>(item);
			return color->color;
		}
		item = item->parent;
	}
	return p_default_color;
}
Color RichTextLabel::_find_outline_color(Item *p_item, const Color &p_default_color) {
	Item *item = p_item;
	while (item) {
		if (item->type == ITEM_OUTLINE_COLOR) {
			ItemOutlineColor *color = static_cast<ItemOutlineColor *>(item);
			return color->color;
		}
		item = item->parent;
	}
	return p_default_color;
}
bool RichTextLabel::_find_underline(Item *p_item) {