fix:add assert if exception occurs

source/dnode/mnode/impl/src/mndConsumer.c

@@ -420,6 +420,7 @@ static int32_t mndProcessMqHbReq(SRpcMsg *pMsg) {
 
     SMqSubscribeObj *pSub = mndAcquireSubscribe(pMnode, pConsumer->cgroup, data->topicName);
     if(pSub == NULL){
+      ASSERT(0);
       continue;
     }
     taosWLockLatch(&pSub->lock);
@@ -515,7 +516,10 @@ static int32_t mndProcessAskEpReq(SRpcMsg *pMsg) {
       char            *topic = taosArrayGetP(pConsumer->currentTopics, i);
       SMqSubscribeObj *pSub = mndAcquireSubscribe(pMnode, pConsumer->cgroup, topic);
       // txn guarantees pSub is created
-      if(pSub == NULL) continue;
+      if(pSub == NULL) {
+        ASSERT(0);
+        continue;
+      }
       taosRLockLatch(&pSub->lock);
 
       SMqSubTopicEp topicEp = {0};
@@ -524,6 +528,7 @@ static int32_t mndProcessAskEpReq(SRpcMsg *pMsg) {
       // 2.1 fetch topic schema
       SMqTopicObj *pTopic = mndAcquireTopic(pMnode, topic);
       if(pTopic == NULL) {
+        ASSERT(0);
         taosRUnLockLatch(&pSub->lock);
         mndReleaseSubscribe(pMnode, pSub);
         continue;