### 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)

}
	k->set_echo(p_echo);
	if (k->get_keycode() == Key::BACKTAB) {
		
		k->set_keycode(Key::TAB);
		k->set_physical_keycode(Key::TAB);
		k->set_shift_pressed(true);
	}
	
	
	if (!k->is_pressed()) {
		if (k->get_keycode() == Key::SHIFT) {
			k->set_shift_pressed(false);
		} else if (k->get_keycode() == Key::CTRL) {
			k->set_ctrl_pressed(false);
		} else if (k->get_keycode() == Key::ALT) {
			k->set_alt_pressed(false);
		} else if (k->get_keycode() == Key::META) {
			k->set_meta_pressed(false);
		}
	}
	bool last_is_pressed = Input::get_singleton()->is_key_pressed(k->get_keycode());
	if (k->is_pressed()) {
		if (last_is_pressed) {
			k->set_echo(true);
		}
	}
	Input::get_singleton()->parse_input_event(k);
}
Atom DisplayServerX11::_process_selection_request_target(Atom p_target, Window p_requestor, Atom p_property, Atom p_selection) const {