### 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)

mbd->set_button_mask(last_button_state);
				mbd->set_pressed(false);
				Input::get_singleton()->parse_input_event(mbd);
			}
		} break;
		case WM_WINDOWPOSCHANGED: {
			Rect2i window_client_rect;
			Rect2i window_rect;
			{
				RECT rect;
				GetClientRect(hWnd, &rect);
				ClientToScreen(hWnd, (POINT *)&rect.left);
				ClientToScreen(hWnd, (POINT *)&rect.right);
				window_client_rect = Rect2i(rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top);
				window_client_rect.position -= _get_screens_origin();
				RECT wrect;
				GetWindowRect(hWnd, &wrect);
				window_rect = Rect2i(wrect.left, wrect.top, wrect.right - wrect.left, wrect.bottom - wrect.top);
				window_rect.position -= _get_screens_origin();
			}
			WINDOWPOS *window_pos_params = (WINDOWPOS *)lParam;
			WindowData &window = windows[window_id];
			bool rect_changed = false;
			if (!(window_pos_params->flags & SWP_NOSIZE) || window_pos_params->flags & SWP_FRAMECHANGED) {
				int screen_id = window_get_current_screen(window_id);
				Size2i screen_size = screen_get_size(screen_id);
				Point2i screen_position = screen_get_position(screen_id);
				window.maximized = false;
				window.minimized = false;
				window.fullscreen = false;