### 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
_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	if ((p_size != Size2()) && ((p_size.x < wd.min_size.x) || (p_size.y < wd.min_size.y))) {
		ERR_PRINT("Maximum window size can't be smaller than minimum window size!");
		return;
	}
	wd.max_size = p_size;
}
Size2i DisplayServerWindows::window_get_max_size(WindowID p_window) const {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_V(!windows.has(p_window), Size2i());
	const WindowData &wd = windows[p_window];
	return wd.max_size;
}
void DisplayServerWindows::window_set_min_size(const Size2i p_size, WindowID p_window) {