When a message has a null field, the `Flatten` SMT does not properly handle this and throws an NPE. Consider this message from Debezium:
Note how `before` is null; this event represents a row was INSERTED and thus there is no `before` state of the row. This results in an NPE:
Here's the connector configuration that was used:
Note that the above configuration sets the delimiter to `_`. The default delimiter is `.`, which is not a valid character within an Avro field, and doing this results in the following exception:
This should probably be addressed in the documentation: when using Avro, set the delimiter to `_` or another alphanumeric character.