### Godot version

4.0.beta12

### System information

Windows 11, RTX 3080

### Issue description

When a Window Node is created with it's Transparent flag set to true and Project Settings --> Display --> Window --> Subwindows --> Embed Subwindows is false, the Window has a black background. By cycling the transparent flag from false and back to true again, during runtime, the window's background then becomes transparent. 

### Steps to reproduce

Attempt to create a Non-embedded Subwindow with a transparent background using the appropriate flags. 

### Minimal reproduction project

Note: this project is from Reddit user [gongpha](https://www.reddit.com/user/gongpha/) and his Reddit post [Learning a Godot 4.0 Window node](https://www.reddit.com/r/godot/comments/xr8yxn/learning_a_godot_40_window_node/)

https://github.com/gongpha/godot4-window-test
RBMap<int, Vector2>::Element *curr = touch_state.find(idx);
	if (!curr) {
		return;
	}
	if (curr->get() == Vector2(p_x, p_y)) {
		return;
	}
	Ref<InputEventScreenDrag> event;
	event.instantiate();
	event->set_window_id(p_window);
	event->set_index(idx);
	event->set_position(Vector2(p_x, p_y));
	event->set_relative(Vector2(p_x, p_y) - curr->get());
	Input::get_singleton()->parse_input_event(event);
	curr->get() = Vector2(p_x, p_y);
}
void DisplayServerWindows::_send_window_event(const WindowData &wd, WindowEvent p_event) {