Steps to reproduce the issue

try to access the params of a menu item using $item->params->get(...)
the item is loaded using
$items = $menu->getItems('menutype', $params->get('menutype'));

Expected result

to get the param value

Actual result

site crash

System information (as much as possible)

it was working in joomla 3, does not work in joomla 4 beta 3

I see in the mod_menu that it uses that :
$itemParams = $item->getParams();

but doing this, it will break all existing layouts from extension where the $item->param is used to get the values.

This is a BIG problem and the $item->params->get('value') shall work in any cases as before

Additional comments

this problem totally crashes the page as soon as the module is published