[Issue 5832][Pulsar IO]Fix npe of debezium delete event (#5876)

Fixes https://github.com/apache/pulsar/issues/5832

Master Issue: https://github.com/apache/pulsar/issues/5832

### Motivation

Currently, in debezium, for delete events, in order to be compatible with Kafka's compaction, each delete event will be followed by a record with a null value. For records with a null value, the null value is not currently processed in pulsar, resulting in an exception of throwing a null pointer. Now, we considered to ignore the null value or use it in combination with pulsar's compaction feature in the future.

![image](https://user-images.githubusercontent.com/1907867/70976050-21cef680-20e6-11ea-963f-56471c915c98.png)
https://debezium.io/documentation/reference/0.10/connectors/mysql.html

### Modifications

* Ignore the record of the null value.
* Add more integrations, such as insert, delete, update.
6 files changed
tree: e4972f90a6950f00be45142dce686d9bad895b8e
  1. distribution/
  2. docker/
  3. tests/