### 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)

}
#endif
				last_timestamp = event.xkey.time;
				
				
				_handle_key_event(window_id, &event.xkey, events, event_index);
			} break;
			case SelectionNotify:
				if (ime_window_event) {
					break;
				}
				if (event.xselection.target == requested) {
					Property p = _read_property(x11_display, windows[window_id].x11_window, XInternAtom(x11_display, "PRIMARY", 0));
					Vector<String> files = String((char *)p.data).split("\r\n", false);
					XFree(p.data);
					for (int i = 0; i < files.size(); i++) {
						files.write[i] = files[i].replace("file:", "").uri_decode();
					}
					if (!windows[window_id].drop_files_callback.is_null()) {
						Variant v = files;
						Variant *vp = &v;
						Variant ret;
						Callable::CallError ce;
						windows[window_id].drop_files_callback.callp((const Variant **)&vp, 1, ret, ce);
					}
					
					XClientMessageEvent m;
					memset(&m, 0, sizeof(m));
					m.type = ClientMessage;
					m.display = x11_display;