### Godot version

4.0.3.stable

### System information

windows 11

### Issue description

fullscreen on the window node is not working and will show up as a windowed.

### Steps to reproduce

disable Embed Subwindows in Project Settings/Display/Window.
create a window node and set its mode to fullscreen.

### Minimal reproduction project

[fullscreen.zip](https://github.com/godotengine/godot/files/11821834/fullscreen.zip)
ERR_READ_THREAD_GUARD_V(Ref<Font>());
	if (!initialized) {
		WARN_PRINT_ONCE("Attempting to access theme items too early; prefer NOTIFICATION_POSTINITIALIZE and NOTIFICATION_THEME_CHANGED");
	}
	if (p_theme_type == StringName() || p_theme_type == get_class_name() || p_theme_type == theme_type_variation) {
		const Ref<Font> *font = theme_font_override.getptr(p_name);
		if (font) {
			return *font;
		}
	}
	if (theme_font_cache.has(p_theme_type) && theme_font_cache[p_theme_type].has(p_name)) {
		return theme_font_cache[p_theme_type][p_name];
	}
	List<StringName> theme_types;
	theme_owner->get_theme_type_dependencies(this, p_theme_type, &theme_types);
	Ref<Font> font = theme_owner->get_theme_item_in_types(Theme::DATA_TYPE_FONT, p_name, theme_types);
	theme_font_cache[p_theme_type][p_name] = font;
	return font;
}
int Window::get_theme_font_size(const StringName &p_name, const StringName &p_theme_type) const {