### 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
encode_uint32(40, &icon_bmp[0]);
	encode_uint32(w, &icon_bmp[4]);
	encode_uint32(h * 2, &icon_bmp[8]);
	encode_uint16(1, &icon_bmp[12]);
	encode_uint16(32, &icon_bmp[14]);
	encode_uint32(BI_RGB, &icon_bmp[16]);
	encode_uint32(w * h * 4, &icon_bmp[20]);
	encode_uint32(0, &icon_bmp[24]);
	encode_uint32(0, &icon_bmp[28]);
	encode_uint32(0, &icon_bmp[32]);
	encode_uint32(0, &icon_bmp[36]);
	uint8_t *wr = &icon_bmp[40];
	const uint8_t *r = icon->get_data().ptr();
	for (int i = 0; i < h; i++) {
		for (int j = 0; j < w; j++) {
			const uint8_t *rpx = &r[((h - i - 1) * w + j) * 4];
			uint8_t *wpx = &wr[(i * w + j) * 4];
			wpx[0] = rpx[2];
			wpx[1] = rpx[1];
			wpx[2] = rpx[0];
			wpx[3] = rpx[3];
		}
	}
	HICON hicon = CreateIconFromResource(icon_bmp, icon_len, TRUE, 0x00030000);
	
	SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_SMALL, (LPARAM)hicon);
	
	SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_BIG, (LPARAM)hicon);
}
void DisplayServerWindows::window_set_vsync_mode(DisplayServer::VSyncMode p_vsync_mode, WindowID p_window) {