### 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)

_touch_event(window_id, false, E.value.x, E.value.y, E.key);
			}
			touch_state.clear();
			bool self_steal = false;
			HWND new_hwnd = (HWND)wParam;
			if (IsWindow(new_hwnd)) {
				self_steal = true;
			}
			if (!self_steal) {
				if (OS::get_singleton()->get_main_loop()) {
					OS::get_singleton()->get_main_loop()->notification(MainLoop::NOTIFICATION_APPLICATION_FOCUS_OUT);
				}
				app_focused = false;
			}
		} break;
		case WM_ACTIVATE: { 
			if (!windows[window_id].window_focused) {
				_process_activate_event(window_id, wParam, lParam);
			} else {
				windows[window_id].saved_wparam = wParam;
				windows[window_id].saved_lparam = lParam;
				
				windows[window_id].focus_timer_id = SetTimer(windows[window_id].hWnd, 2, USER_TIMER_MINIMUM, (TIMERPROC) nullptr);
			}
			if (wParam != WA_INACTIVE) {
				track_mouse_leave_event(hWnd);
			}
			return 0; 
		} break;
		case WM_GETMINMAXINFO: {