### 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 (mouse_mode == MOUSE_MODE_CAPTURED || mouse_mode == MOUSE_MODE_CONFINED || mouse_mode == MOUSE_MODE_CONFINED_HIDDEN) {
					RECT crect;
					GetClientRect(window.hWnd, &crect);
					ClientToScreen(window.hWnd, (POINT *)&crect.left);
					ClientToScreen(window.hWnd, (POINT *)&crect.right);
					ClipCursor(&crect);
				}
			}
			
			
			return 0;
		} break;
		case WM_ENTERSIZEMOVE: {
			Input::get_singleton()->release_pressed_events();
			windows[window_id].move_timer_id = SetTimer(windows[window_id].hWnd, 1, USER_TIMER_MINIMUM, (TIMERPROC) nullptr);
		} break;
		case WM_EXITSIZEMOVE: {
			KillTimer(windows[window_id].hWnd, windows[window_id].move_timer_id);
		} break;
		case WM_TIMER: {
			if (wParam == windows[window_id].move_timer_id) {
				_process_key_events();
				if (!Main::is_iterating()) {
					Main::iteration();
				}
			} else if (wParam == windows[window_id].focus_timer_id) {
				_process_activate_event(window_id, windows[window_id].saved_wparam, windows[window_id].saved_lparam);
				KillTimer(windows[window_id].hWnd, wParam);