TypeError: implode(): Argument #1 ($array) must be of type array

Problem/Motivation

When Image optimizer is enabled.

TypeError: implode(): Argument #1 ($array) must be of type array, string given in implode() (line 1158 of /app/web/core/lib/Drupal/Core/Form/FormState.php).
...

#1 /app/web/modules/contrib/fastly/src/Form/ImageOptimizerForm.php(243): Drupal\Core\Form\FormState->setError()

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes