After updating to Magento 2.2.6, the following error is output

Question

After updating to Magento 2.2.6, the following error is output.

Go to

Backend> System> Permission (All Users)> Users

Clicking each line... etc. outputs an error.

The following is an error message.

Exception # 0 (Exception): Warning: Illegal offset type in /var/www/html/multistore/vendor/magento/module-backend/Block/Widget/Tabs.php on line 306

Answer 1

I am still debugging on my development server, so far I found that changing the file /vendor/magento/module-backend/Block/Widget/Tabs.php - line 306

$grandPosition = $orderByIdentity[$tab->getAfter()]->getPosition();

to

$grandPosition = $orderByIdentity[(string)$tab->getAfter()]->getPosition();

resolved the issue for me.

This is not a fix as it involves editing the core magento files, but indicates that it could be an issue with an extension that adds tabs to the user view - if you have any extensions that add tabs to this view, you could try contacting the vendor or disabling the module.