### 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)

} break;
			case ConfigureNotify: {
				DEBUG_LOG_X11("[%u] ConfigureNotify window=%lu (%u), event=%lu, above=%lu, override_redirect=%u \n", frame, event.xconfigure.window, window_id, event.xconfigure.event, event.xconfigure.above, event.xconfigure.override_redirect);
				if (event.xconfigure.window == windows[window_id].x11_xim_window) {
					break;
				}
				const WindowData &wd = windows[window_id];
				XWindowAttributes xwa;
				XSync(x11_display, False);
				XGetWindowAttributes(x11_display, wd.x11_window, &xwa);
				
				
				
				if ((xwa.map_state == IsViewable) && !wd.no_focus && !wd.is_popup) {
					XSetInputFocus(x11_display, wd.x11_window, RevertToPointerRoot, CurrentTime);
				}
				_window_changed(&event);
			} break;
			case ButtonPress:
			case ButtonRelease: {
				if (ime_window_event || ignore_events) {
					break;
				}
				
				last_timestamp = event.xbutton.time;
				if (mouse_mode == MOUSE_MODE_CAPTURED) {
					event.xbutton.x = last_mouse_pos.x;
					event.xbutton.y = last_mouse_pos.y;
				}
				Ref<InputEventMouseButton> mb;