### 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_physical_keycode(Key::TAB);
						k->set_shift_pressed(true);
					}
					Input::get_singleton()->parse_input_event(k);
				}
				return;
			}
		}
#endif
	}
	
	
	
	Key keycode = KeyMappingX11::get_keycode(keysym_keycode);
	Key physical_keycode = KeyMappingX11::get_scancode(xkeyevent->keycode);
	
	
	
	
	char32_t unicode = keysym_unicode > 0 ? KeyMappingX11::get_unicode_from_keysym(keysym_unicode) : 0;
	
	
	
	
	
	
	
	bool keypress = xkeyevent->type == KeyPress;
	if (physical_keycode == Key::NONE && keycode == Key::NONE && unicode == 0) {
		return;