### 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
ERR_FAIL_COND_V(!tts, TypedArray<Dictionary>());
	return tts->get_voices();
}
void DisplayServerWindows::tts_speak(const String &p_text, const String &p_voice, int p_volume, float p_pitch, float p_rate, int p_utterance_id, bool p_interrupt) {
	ERR_FAIL_COND(!tts);
	tts->speak(p_text, p_voice, p_volume, p_pitch, p_rate, p_utterance_id, p_interrupt);
}
void DisplayServerWindows::tts_pause() {
	ERR_FAIL_COND(!tts);
	tts->pause();
}
void DisplayServerWindows::tts_resume() {
	ERR_FAIL_COND(!tts);
	tts->resume();
}
void DisplayServerWindows::tts_stop() {
	ERR_FAIL_COND(!tts);
	tts->stop();
}
void DisplayServerWindows::mouse_set_mode(MouseMode p_mode) {
	_THREAD_SAFE_METHOD_
	if (mouse_mode == p_mode) {
		
		return;
	}
	mouse_mode = p_mode;
	_set_mouse_mode_impl(p_mode);
}
DisplayServer::MouseMode DisplayServerWindows::mouse_get_mode() const {