[Bug] Fix gRPC response message NPE

[dingshuangxi888]

Before Creating the Bug Report

• I found a bug, not just asking a question, which should be created in GitHub Discussions.

• I have searched the GitHub Issues and GitHub Discussions of this repository and believe that this is not a duplicate.

• I have confirmed that this bug belongs to the current repository, not other repositories of RocketMQ.

Runtime platform environment

linux

RocketMQ version

develop

JDK Version

Java8

Describe the Bug

When a system exception occurs in gRPC, such as a NullPointerException (NPE), the Response returned to the client may have its message set to null, resulting in another NPE. In such cases, the client cannot receive the response.

Steps to Reproduce

When call gRPC sevice, and throw NPE, the client can not get the response.

What Did You Expect to See?

If NPE occurs, it can returns the response.

What Did You See Instead?

If NPE occurs, it can returns the response.

Additional Context

No response