### 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)

SetCursorPos(pos.x, pos.y);
			SetCapture(wd.hWnd);
			_register_raw_input_devices(window_id);
		}
	} else {
		
		ReleaseCapture();
		ClipCursor(nullptr);
		_register_raw_input_devices(INVALID_WINDOW_ID);
	}
	if (p_mode == MOUSE_MODE_HIDDEN || p_mode == MOUSE_MODE_CAPTURED || p_mode == MOUSE_MODE_CONFINED_HIDDEN) {
		if (hCursor == nullptr) {
			hCursor = SetCursor(nullptr);
		} else {
			SetCursor(nullptr);
		}
	} else {
		CursorShape c = cursor_shape;
		cursor_shape = CURSOR_MAX;
		cursor_set_shape(c);
	}
}
DisplayServer::WindowID DisplayServerWindows::_get_focused_window_or_popup() const {
	const List<WindowID>::Element *E = popup_list.back();
	if (E) {
		return E->get();
	}
	return last_focused_window;
}
void DisplayServerWindows::_register_raw_input_devices(WindowID p_target_window) {