Use Enum.getDeclaringClass() to avoid NPE in comparing enums

[blindpirate]

Context

Fix #1861 , which is due to a misuse of Enum.getClass().getCanonicalName(). In this scenario, Enum.getDeclaringClass() should be used.

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• Review Contribution Guidelines
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• Provide unit tests (under <subproject>/src/test) to verify logic
• Ensure that tests pass locally: ./gradlew quickCheck <impacted-subproject>:check

[big-guy]

Thanks, this will be in the next release.