fix:pSub is null

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

@@ -646,8 +646,9 @@ int32_t mndProcessSubscribeReq(SRpcMsg *pMsg) {
   int32_t newTopicNum = taosArrayGetSize(pTopicList);
   for(int i = 0; i < newTopicNum; i++){
     SMqSubscribeObj *pSub = mndAcquireSubscribe(pMnode, (const char*)cgroup, (const char*)taosArrayGetP(pTopicList, i));
+    if(pSub == NULL) continue;
     taosRLockLatch(&pSub->lock);
-    if(pSub != NULL && taosHashGetSize(pSub->consumerHash) > MND_MAX_GROUP_PER_TOPIC){
+    if(taosHashGetSize(pSub->consumerHash) > MND_MAX_GROUP_PER_TOPIC){
       terrno = TSDB_CODE_TMQ_GROUP_OUT_OF_RANGE;
       code = terrno;
       taosRUnLockLatch(&pSub->lock);