thank you, but its not working. Only white screen now.

In line 437-444 Ive found:
// Get the id of the active menu item
$menu = $this->getMenu();
$item = $menu->getActive();

if (!$item)
{
$item = $menu->getItem($this->input->getInt('Itemid', null));
}

And I changed it to:
// Get the id of the active menu item
$menu = $this->getMenu();
$item = $menu->getActive();

if (!$item)
{
//added new line
$this->route();

$item = $menu->getItem($this->input->getInt('Itemid', null));
}

unfortunately no success ...

Trying to post your question in joomla support forum.

joomfreak