### 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)

}
			if (event.xany.window == E.value.x11_xim_window) {
				window_id = E.key;
				ime_window_event = true;
				break;
			}
		}
		if (XGetEventData(x11_display, &event.xcookie)) {
			if (event.xcookie.type == GenericEvent && event.xcookie.extension == xi.opcode) {
				XIDeviceEvent *event_data = (XIDeviceEvent *)event.xcookie.data;
				int index = event_data->detail;
				Vector2 pos = Vector2(event_data->event_x, event_data->event_y);
				switch (event_data->evtype) {
					case XI_HierarchyChanged:
					case XI_DeviceChanged: {
						_refresh_device_info();
					} break;
					case XI_RawMotion: {
						if (ime_window_event || ignore_events) {
							break;
						}
						XIRawEvent *raw_event = (XIRawEvent *)event_data;
						int device_id = raw_event->sourceid;
						
						
						
						if (raw_event->valuators.mask_len <= 0) {
							break;
						}
						const double *values = raw_event->raw_values;