[Bug] Proxy：开启 namesrv的orderMessageEnable 后 broker 整组下线时 TopicRouteWrapper#getMasterAddr 空指针，导致该 topic 整条路由加载失败

Start in proxy/src/main/java/org/apache/rocketmq/proxy/service/route/TopicRouteWrapper.java at getMasterAddr and inspect getMasterAddrPrefer as well. Trace how TopicRouteService.buildMessageQueueView handles a missing broker after the route cache expires. Done means an absent broker no longer causes an NPE or prevents the topic route from being built; reproduce with the orderMessageEnable and broker shutdown steps described.

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

TopicRouteWrapper#getMasterAddr 对 brokerNameRouteData.get(brokerName) 的返回值未做判空，
直接链式调用 .getBrokerAddrs()。当某个 broker 组从 NameServer 完整注销（整组下线/单副本部署
broker 进程退出）后，brokerNameRouteData 中已无该 brokerName，get() 返回 null，
随后即抛 NPE。

// proxy/src/main/java/org/apache/rocketmq/proxy/service/route/TopicRouteWrapper.java:45-47
public String getMasterAddr(String brokerName) {
    return this.brokerNameRouteData.get(brokerName).getBrokerAddrs().get(MixAll.MASTER_ID);
    //                   ^^^^^^^^^^^^^^^^^^^^^^^^^ 整组注销后为 null，此处直接 NPE
}

RocketMQ version

rocketmq 5.5.0

JDK Version

java 11

Describe the Bug

111

Steps to Reproduce

前两步即触发条件中的"开关 + KV"，不可省略——省略任何一步则走动态分支，无法复现。

1. namesrv 配置 orderMessageEnable=true；两个 broker 组（broker-a、broker-b，单副本即可）；
2. 创建 topic 并写入静态快照：
   mqadmin updateOrderTopicKvConfig -n <ns> -t T -o "broker-a:8;broker-b:8"
3. 启动 proxy，经 proxy 对 T 发送若干消息（建立路由缓存）；
4. 停止使用该 topic 5 分钟以上（让 Caffeine 条目过期），然后整组杀掉 broker-b；
5. 再次经 proxy 访问 topic T（发送或查询路由）。

实测结果（proxy 日志）：

java.lang.NullPointerException
    at org.apache.rocketmq.proxy.service.route.TopicRouteWrapper.getMasterAddr(TopicRouteWrapper.java:46)
    at org.apache.rocketmq.proxy.service.route.TopicRouteService.buildMessageQueueView(TopicRouteService.java:203)
    at org.apache.rocketmq.proxy.service.route.TopicRouteService$1.reload(TopicRouteService.java:94)
    at org.apache.rocketmq.proxy.service.route.TopicRouteService$1.load(TopicRouteService.java:81)
    at org.apache.rocketmq.proxy.service.route.MessageQueueView.<init>(MessageQueueView.java:41)

broker 下线期间，T 的每次冷加载都抛 NPE，整 topic 路由不可用；broker 恢复后自愈。

What Did You Expect to See?

地址查找应空安全：brokerName 查不到时返回 null（或空 Optional），由调用方决定如何处理
（orderTopicConf 分支至少不应让整条路由构建失败）。一个最小修复是在 getMasterAddr 内判空：

public String getMasterAddr(String brokerName) {
    BrokerData brokerData = this.brokerNameRouteData.get(brokerName);
    if (brokerData == null) {
        return null;
    }
    return brokerData.getBrokerAddrs().get(MixAll.MASTER_ID);
}

（getMasterAddrPrefer 同样的裸解引用也建议一并处理。）

What Did You See Instead?

111

Additional Context

No response