### 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_
	MSG msg;
	if (!drop_events) {
		joypad->process_joypads();
	}
	while (PeekMessageW(&msg, nullptr, 0, 0, PM_REMOVE)) {
		TranslateMessage(&msg);
		DispatchMessageW(&msg);
	}
	if (!drop_events) {
		_process_key_events();
		Input::get_singleton()->flush_buffered_events();
	}
}
void DisplayServerWindows::force_process_and_drop_events() {