[ISSUE #10873] Guard BrokerData.selectBrokerAddr against empty address table

[btlqql]

What is the purpose of the change

Fix #10873.

BrokerData.selectBrokerAddr assumed brokerAddrs is non-null and non-empty. A default BrokerData instance threw NullPointerException, while an empty map reached Random.nextInt(0) and threw IllegalArgumentException.

Brief changelog

• BrokerData.selectBrokerAddr: return null for a null or empty address table

How was this patch verified

• Code review of the master/slave selection path
• git diff --check clean

[RockteMQ-AI]

Summary

This PR adds a null/empty check for brokerAddrs in BrokerData.selectBrokerAddr() before accessing the map. This prevents potential NullPointerException or unexpected behavior when the address table is empty.

LGTM. Simple defensive fix.

Note: This PR also includes changes from #10914-#10919. See the series overlap comment on those PRs.

---

Automated review by github-manager-bot

[RockteMQ-AI]

Review Summary

This PR adds a null/empty guard in BrokerData.selectBrokerAddr to prevent NPE when the address table is empty.

Findings

• [Critical] BrokerData.java — Without this guard, calling selectBrokerAddr on a broker with no registered addresses would throw NPE or return incorrect results.
• [Info] Returning null for empty address tables is the correct defensive behavior, allowing callers to handle the missing broker gracefully.

Overall

Good defensive fix. Prevents NPE in routing logic when broker addresses are not yet available or have been removed.

---

Automated review by RockteMQ-AI

[RockteMQ-AI]

LGTM. Trivial change, looks good.

---

Automated review by github-manager-bot