Json/valid cols

[Koustavd18]

Fix: This PR changes the JSON view to show the keys with a valid value

[balaji-jr]

To find the valid headers you are iterating the log object twice which is unnecessary.
log[header] === null ? 'null': And not clear why this is needed and why its included in the finding valid headers logic ?

[balaji-jr]

Not sure why this is still needed.
If you are iterating over a log object, why you'd want to test whether its empty or not ?

[balaji-jr]

I will address the remaining changes on #303

[nikhilsinhaparseable]

looks good