Backend admin error when opening a content-page

After updating to v1.7.49.5 - Admin v1.10.50, I can no longer open any content pages in the backend.

Error: An exception has been thrown during the rendering of a template ("Array to string conversion"). Twig\Error\RuntimeError - \user\plugins\form\templates\forms\fields\select\select.html.twig:72.

Here line 72:
`{{ item_value|t|raw }}`

- All plugins have been updated.
- The frontend is not affected.

Thank you for the quick help. Thomas

Reproduce the failure by opening a content page in the backend after the reported updates. Start at user/plugins/form/templates/forms/fields/select/select.html.twig line 72 and trace which value reaches the option rendering; done means backend content pages open without the Array to string conversion error while the frontend remains unaffected.

Written by the indexing model from the issue text.