Fix multi-topics-consumer new topic listeners stuck in paused state (#481)

This was introduced in v3.7.0 via #447, which contained a change that attempted to fix an issue where a pre-mature ack of a message before a multi-topic subscriber was ready could have caused a crash.  To fix the original bug, all multi-topic subscriptions are started with their message listener paused. They later get un-paused once all topics are successfully subscribed and connected.  However, on a regex subscription when new topics are discovered, they also start in a paused state, and there's no mechanism to resume them.  Hence, they get stuck, and no messages for new topics will be processed.

This change adds a call to resume any new listeners after new topics are added.

Author: oversearch

lib/PatternMultiTopicsConsumerImpl.cc

@@ -118,6 +118,9 @@ void PatternMultiTopicsConsumerImpl::timerGetTopicsOfNamespace(const Result resu
     // callback method when added topics all subscribed.
     ResultCallback topicsAddedCallback = [this, topicsRemoved, topicsRemovedCallback](Result result) {
         if (result == ResultOk) {
+            if (messageListener_) {
+                resumeMessageListener();
+            }
             // call to unsubscribe all removed topics.
             onTopicsRemoved(topicsRemoved, topicsRemovedCallback);
         } else {