JSON Logs with Multiple undefined Properties not Appearing in Loggly

[matthewbordas]

I noticed something strange happening today with our JSON logs being sent to Loggly via Winston. They have 8 properties and if at least 2 of them are undefined, then the log doesn't appear in Loggly. Also, when this case happens, the LogglerInstance.log method returns undefined, but normally it returns the LoggerInstance. I couldn't find this documented anywhere in this repo or on Loggly. Is this expected input sanitation behavior or something - for a JSON log with multiple undefined properties to be ignored? If I change the default value from undefined to null, then it works fine. So logs with multiple null properties show up, but not logs with multiple undefined properties?