### 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
drop_events = false;
	key_event_pos = 0;
	alt_mem = false;
	gr_mem = false;
	shift_mem = false;
	control_mem = false;
	meta_mem = false;
	hInstance = static_cast<OS_Windows *>(OS::get_singleton())->get_hinstance();
	pressrc = 0;
	old_invalid = true;
	mouse_mode = MOUSE_MODE_VISIBLE;
	rendering_driver = p_rendering_driver;
	
	tts = memnew(TTS_Windows);
	
	screen_set_keep_on(GLOBAL_GET("display/window/energy_saving/keep_screen_on"));
	
	OSVERSIONINFOW os_ver;
	ZeroMemory(&os_ver, sizeof(OSVERSIONINFOW));
	os_ver.dwOSVersionInfoSize = sizeof(OSVERSIONINFOW);
	HMODULE nt_lib = LoadLibraryW(L"ntdll.dll");
	if (nt_lib) {
		RtlGetVersionPtr RtlGetVersion = (RtlGetVersionPtr)GetProcAddress(nt_lib, "RtlGetVersion");
		if (RtlGetVersion) {