After an update to Joomla 3.8.10 some users are getting errors and they can not use the menu.

Screen pops up the following error message

Cannot Use Object Of Type StdClass As Array

The solution is quite simple:

Edit the file "helix3.php" (plugins/system/helix3/helix3.php)

And add the following code on 50 line:

if (is_object($data)) {

           $data = (array)$data;

}

After the line: JForm::addFormPath(JPATH PLUGINS.'...)

And before the line: if ($form->getName()=='com_menus.item')