### 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
MoveWindow(wd.hWnd, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, TRUE);
		if (restore_mouse_trails > 1) {
			SystemParametersInfoA(SPI_SETMOUSETRAILS, restore_mouse_trails, 0, 0);
			restore_mouse_trails = 0;
		}
	} else if (p_mode == WINDOW_MODE_WINDOWED) {
		ShowWindow(wd.hWnd, SW_RESTORE);
		wd.maximized = false;
		wd.minimized = false;
	}
	if (p_mode == WINDOW_MODE_MAXIMIZED) {
		ShowWindow(wd.hWnd, SW_MAXIMIZE);
		wd.maximized = true;
		wd.minimized = false;
	}
	if (p_mode == WINDOW_MODE_MINIMIZED) {
		ShowWindow(wd.hWnd, SW_MINIMIZE);
		wd.maximized = false;
		wd.minimized = true;
	}
	if (p_mode == WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
		wd.multiwindow_fs = false;
		_update_window_style(p_window, false);
	} else {
		wd.multiwindow_fs = true;
		_update_window_style(p_window, false);
	}
	if ((p_mode == WINDOW_MODE_FULLSCREEN || p_mode == WINDOW_MODE_EXCLUSIVE_FULLSCREEN) && !wd.fullscreen) {
		if (wd.minimized) {
			ShowWindow(wd.hWnd, SW_RESTORE);