Fix pipeline failures on next minor (phpstan + phpunit)

Problem/Motivation

The pipeline reports failures in the next minor (phpstan + phpunit), see for example https://git.drupalcode.org/project/diff/-/pipelines/540492

Proposed resolution

Fix pipeline failures on next minor (phpstan + phpunit)

Remaining tasks

1. Write a merge request
2. Review
3. Commit

User interface changes

To be determined.

API changes

To be determined.

Data model changes

To be determined.