tree 0fb745664dbc08b81f911009a48f97c047108743
parent 3234e14128001cc853d7fdfe4db787cf14f994b9
author Neng Lu <nlu@streamnative.io> 1589868702 -0700
committer GitHub <noreply@github.com> 1589868702 +0800

[Issue 4803][client] return null if the message value/data is not set by producer (#6379)

Fixes #4803 

### Motivation
Allow the typed consumer receive messages with `null` value if the producer sends message without payload.

### Modifications
- add a flag in `MessageMetadata` to indicate if the payload is set when the message is created
- check and return `null` if the flag is not set when reading data from a message