fix NPE for records

[amishra-u]

What's changed?

• fixes Joda Recipe NullpointerException when visting Java Records #635

With Java Records, class variables are defined as constructor parameters, that was previously unhandled.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Thanks for the quick fix here @amishra-u !