### 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;
					}
					if (event_index + 1 < events.size()) {
						const XEvent &next_event = events[event_index + 1];
						if (next_event.type == MotionNotify) {
							++event_index;
							event = next_event;
						} else {
							break;
						}
					} else {
						break;
					}
				}
				last_timestamp = event.xmotion.time;
				
				
				
				Point2i pos(event.xmotion.x, event.xmotion.y);
				
				bool filter = false;
				
				if (xi.state.size() && Vector2(pos).distance_squared_to(xi.mouse_pos_to_filter) < 2) {
					filter = true;
				}
				
				xi.mouse_pos_to_filter = Vector2(1e10, 1e10);
				if (filter) {
					break;
				}