[fix][broker]Fix NonPersistentDispatcherMultipleConsumers ArrayIndexO…

…utOfBoundsException (#21856)

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/nonpersistent/NonPersistentDispatcherMultipleConsumers.java

@@ -191,7 +191,7 @@ public RedeliveryTracker getRedeliveryTracker() {
     }
 
     @Override
-    public void sendMessages(List<Entry> entries) {
+    public synchronized void sendMessages(List<Entry> entries) {
         Consumer consumer = TOTAL_AVAILABLE_PERMITS_UPDATER.get(this) > 0 ? getNextConsumer() : null;
         if (consumer != null) {
             SendMessageInfo sendMessageInfo = SendMessageInfo.getThreadLocal();