Github user MikeThomsen commented on the issue:
https://github.com/apache/nifi/pull/2672
@pvillard31 @joewitt Could one of you do a code review on this? It aims to
roll back a little of the new testing behavior that breaks
evaluateExpressionLanguage(FlowFile) when the input is null. The work around to
get the testing behavior to match the live behavior is [pretty
hackish](https://issues.apache.org/jira/browse/NIFI-5145).---
