patch field being String in FileComparison causing compareCommit to crash

[rojsrojs]

Follow up from #746.

This is generally not true:

I noticed, if a very large change has been made (like 2000 row change of a file), which still has status modified, the patch field won't appear in that case either, which causes JsonParsingError(Invalid message body: Could not decode JSON: {..} error message.

Patch being Option[String] in all scenarios solves this issue.