[PR] [ISSUE #D4] Fix getConsumeStatus NPE for a group absent from ConsumerManager [rocketmq]

["zjncs (via GitHub)" <gi...@apache.org>]

zjncs opened a new pull request, #11110:
URL: https://github.com/apache/rocketmq/pull/11110

   ## Motivation
   
   `Broker2Client.getConsumeStatus` dereferences the consumer group info before checking it:
   
   ```java
   ConcurrentMap<Channel, ClientChannelInfo> channelInfoTable =
       this.brokerController.getConsumerManager().getConsumerGroupInfo(group).getChannelInfoTable();
   if (null == channelInfoTable || channelInfoTable.isEmpty()) {
       // "No Any Consumer online in the consumer group: [%s]"
   }
   ```
   
   When the queried group has no consumer registered on this broker — the normal situation for an offline group — `getConsumerGroupInfo(group)` returns null and the method throws `NullPointerException` before reaching the error branch that was written for exactly this case. The sibling `resetOffset` method checks the group info for null first.
   
   Reached from `mqadmin getConsumerStatus` (`INVOKE_BROKER_TO_GET_CONSUMER_STATUS` → `AdminBrokerProcessor.getConsumerStatus` → here), the NPE surfaces to the admin as a bare SYSTEM_ERROR with a null-pointer remark instead of the intended message.
   
   ## Modification
   
   Fetch the `ConsumerGroupInfo` first; enter the existing "No Any Consumer online" branch when it is null or its channel table is empty; read the channel table only afterwards.
   
   ## Test Evidence
   
   Fail-before (unpatched develop, new regression test):
   
   ```
   mvn -q -pl broker test -Dtest='Broker2ClientTest#testGetConsumeStatusGroupNotRegistered'
   Tests run: 1, Errors: 1 - NullPointerException: Cannot invoke "ConsumerGroupInfo.getChannelInfoTable()"
   ```
   
   Pass-after (full class):
   
   ```
   mvn -q -pl broker test -Dtest='Broker2ClientTest'
   Tests run: 9, Failures: 0, Errors: 0, Skipped: 0
   ```
   
   No associated issue (self-discovered during a broker-module self-audit).


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