### 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)

WindowRect.left = wpos.x;
		WindowRect.right = wpos.x + p_rect.size.x;
		WindowRect.top = wpos.y;
		WindowRect.bottom = wpos.y + p_rect.size.y;
	}
	Point2i offset = _get_screens_origin();
	WindowRect.left += offset.x;
	WindowRect.right += offset.x;
	WindowRect.top += offset.y;
	WindowRect.bottom += offset.y;
	AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);
	WindowID id = window_id_counter;
	{
		WindowData &wd = windows[id];
		wd.hWnd = CreateWindowExW(
				dwExStyle,
				L"Engine", L"",
				dwStyle,
				
				
				WindowRect.left,
				WindowRect.top,
				WindowRect.right - WindowRect.left,
				WindowRect.bottom - WindowRect.top,
				nullptr,
				nullptr,
				hInstance,