### 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
}
		if (width >= big_icon_width) {
			if (colors >= big_icon_cc) {
				big_icon_index = i;
				big_icon_width = width;
				big_icon_cc = colors;
			}
		}
	}
	ERR_FAIL_COND_MSG(big_icon_index == -1, "No valid icons found!");
	if (small_icon_index == -1) {
		WARN_PRINT("No small icon found, reusing " + itos(big_icon_width) + "x" + itos(big_icon_width) + " @" + itos(big_icon_cc) + " icon!");
		small_icon_index = big_icon_index;
		small_icon_cc = big_icon_cc;
	}
	
	DWORD bytecount_big = icon_dir->idEntries[big_icon_index].dwBytesInRes;
	Vector<uint8_t> data_big;
	data_big.resize(bytecount_big);
	pos = icon_dir->idEntries[big_icon_index].dwImageOffset;
	f->seek(pos);
	f->get_buffer((uint8_t *)&data_big.write[0], bytecount_big);
	HICON icon_big = CreateIconFromResource((PBYTE)&data_big.write[0], bytecount_big, TRUE, 0x00030000);
	ERR_FAIL_COND_MSG(!icon_big, "Could not create " + itos(big_icon_width) + "x" + itos(big_icon_width) + " @" + itos(big_icon_cc) + " icon, error: " + format_error_message(GetLastError()) + ".");
	
	DWORD bytecount_small = icon_dir->idEntries[small_icon_index].dwBytesInRes;
	Vector<uint8_t> data_small;
	data_small.resize(bytecount_small);
	pos = icon_dir->idEntries[small_icon_index].dwImageOffset;
	f->seek(pos);