### 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
switch (uMsg) {
		case WM_GETMINMAXINFO: {
			
			
			
		} break;
		case WM_NCCREATE: {
			
			
			CREATESTRUCTW *pCreate = (CREATESTRUCTW *)lParam;
			WindowData *pWindowData = reinterpret_cast<WindowData *>(pCreate->lpCreateParams);
			
			pWindowData->hWnd = hWnd;
		} break;
		default: {
			
			
			
			ERR_PRINT_ONCE(vformat("Unexpected window message 0x%x received for window we cannot recognize in our collection; sequence error.", uMsg));
		} break;
	}
	if (user_proc) {
		return CallWindowProcW(user_proc, hWnd, uMsg, wParam, lParam);
	}
	return DefWindowProcW(hWnd, uMsg, wParam, lParam);
}
LRESULT DisplayServerWindows::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {