https://issues.apache.org/jira/browse/AMQ-6375

Quick fix the build after broken by previous commit on this issue, no
actual stats tracking implemented in LevelDB by this commit.

activemq-leveldb-store/src/main/scala/org/apache/activemq/leveldb/LevelDBStore.scala

@@ -901,6 +901,12 @@ class LevelDBStore extends LockableServiceSupport with BrokerServiceAware with P
       super.asyncAddQueueMessage(context, message, false)
     }
 
+    var stats = new MessageStoreSubscriptionStatistics(false)
+
+    def getMessageStoreSubStatistics: MessageStoreSubscriptionStatistics = {
+        stats;
+    }
+
     def subscription_count = subscriptions.synchronized {
       subscriptions.size
     }