### Godot version

Godot Engine v4.0.stable.official.92bee43ad

### System information

Windows 10

### Issue description

The documentation states that passing ```null``` into the image parameter of ```set_custom_mouse_cursor``` will change it back to the system cursor, however I find that it removes the cursor's image entirely, rather than setting it to the system's cursor.


### Steps to reproduce

```var isimage = false
var theimage = load("res://final.png")

func _on_my_button_pressed():
    if isimage == false:
        Input.set_custom_mouse_cursor(theimage, Input.CURSOR_ARROW, Vector2(16,16))
        isimage = true
        
    else:
        Input.set_custom_mouse_cursor(null)
        isimage = false```

When the button is pressed, the cursor is meant to change to the new cursor. When it has been pressed a second time, it changes back to the default cursor. However, upon pressing it a second time, it simply disappears. The cursor becomes visible again when the cursor exits and re-enters the window.

### Minimal reproduction project

[null mouse.zip](https://github.com/godotengine/godot/files/10901969/null.mouse.zip)

ERR_FAIL_COND(!windows.has(p_id));
	WindowData &wd = windows[p_id];
	popup_open(p_id);
	if (p_id != MAIN_WINDOW_ID) {
		_update_window_style(p_id);
	}
	if (wd.maximized) {
		ShowWindow(wd.hWnd, SW_SHOWMAXIMIZED);
		SetForegroundWindow(wd.hWnd); 
		SetFocus(wd.hWnd); 
	} else if (wd.minimized) {
		ShowWindow(wd.hWnd, SW_SHOWMINIMIZED);
	} else if (wd.no_focus) {
		
		ShowWindow(wd.hWnd, SW_SHOWNA);
	} else if (wd.is_popup) {
		ShowWindow(wd.hWnd, SW_SHOWNA);
		SetFocus(wd.hWnd); 
	} else {
		ShowWindow(wd.hWnd, SW_SHOW);
		SetForegroundWindow(wd.hWnd); 
		SetFocus(wd.hWnd); 
	}
	if (wd.always_on_top) {
		SetWindowPos(wd.hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_FRAMECHANGED | SWP_NOMOVE | SWP_NOSIZE | ((wd.no_focus || wd.is_popup) ? SWP_NOACTIVATE : 0));
	}
}
void DisplayServerWindows::delete_sub_window(WindowID p_window) {