Fix NPE when reading json array with incomplete rows

[ryancerf]

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Description

Fixes #588

Checks whether a json key exists before getting attempting to get it. If the key does not exist add missing a value.

Testing

Yes

[benmccann]

LGTM. Thanks for this

Have you run mvn compile on the command line? I think the formatting doesn't quite match what I'd expect the Google formatting plugin to produce

[ryancerf]

I did not run mvn compile. I can run it in the future. I thought you had the formatter as a post commit hook.