NIFI-6963: Fix ValidateRecord handling of missing required array fields

[mattyb149]

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Description of PR

The default value for array fields was always being set even if not specified in the schema

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[pvillard31]

Hey @mattyb149 - it looks good to me. Do you mind adding a unit test using the default value in the schema?

[markap14]

Looks like @pvillard31 requested that you add an additional unit test. From the code perspective, though, I'm a +1 as well.