Expose `MustBeClosedChecker` exception

[uhafner]

[github-actions[bot]]

:mortar_board: Quality Checks - 200 of 400

:vertical_traffic_light: JUnit - 100 of 100

0 tests passed

:paw_prints: JaCoCo - 0 of 100

0% Covered , 100% Missed

:microbe: PIT - 0 of 100

0% Killed , 100% Survived

:warning: Warnings - 100 of 100

no warnings found

:construction: Error Messages

Autograding GitHub Action Errors:
No matching report files found when using pattern '**/target/*-reports/TEST*.xml'! Configuration error for 'Unittests'?
No matching report files found when using pattern '**/target/site/jacoco/jacoco.xml'! Configuration error for 'Line Coverage'?
No matching report files found when using pattern '**/target/site/jacoco/jacoco.xml'! Configuration error for 'Branch Coverage'?
No matching report files found when using pattern '**/target/pit-reports/mutations.xml'! Configuration error for 'Mutation Coverage'?
No matching report files found when using pattern '**/target/checkstyle-result.xml'! Configuration error for 'CheckStyle'?
No matching report files found when using pattern '**/target/pmd.xml'! Configuration error for 'PMD'?
No matching report files found when using pattern '**/target/spotbugsXml.xml'! Configuration error for 'SpotBugs'?

More details are available in the GitHub Checks Result.