fix two bugs

1. crash when retrieve data
2. invalid read when query a super table which has no sub tables

src/client/src/tscAsync.c

@@ -235,7 +235,7 @@ void taos_fetch_rows_a(TAOS_RES *taosa, void (*fp)(void *, TAOS_RES *, int), voi
         (*pSql->fetchFp)(param, pSql, 0);
       }
       return;
-    } else if (pCmd->command == TSDB_SQL_RETRIEVE) {
+    } else if (pCmd->command == TSDB_SQL_RETRIEVE || pCmd->command == TSDB_SQL_RETRIEVE_LOCALMERGE) {
       // in case of show command, return no data
       (*pSql->fetchFp)(param, pSql, 0);
     } else {

src/client/src/tscServer.c

@@ -46,10 +46,13 @@ static int32_t minMsgSize() { return tsRpcHeadSize + 100; }
 
 static void tscSetDnodeIpList(SSqlObj* pSql, SCMVgroupInfo* pVgroupInfo) {
   SRpcIpSet* pIpList = &pSql->ipList;
-  
-  pIpList->numOfIps = pVgroupInfo->numOfIps;
   pIpList->inUse    = 0;
+  if (pVgroupInfo == NULL) {
+    pIpList->numOfIps = 0;
+    return;
+  }
   
+  pIpList->numOfIps = pVgroupInfo->numOfIps;
   for(int32_t i = 0; i < pVgroupInfo->numOfIps; ++i) {
     strcpy(pIpList->fqdn[i], pVgroupInfo->ipAddr[i].fqdn);
     pIpList->port[i] = pVgroupInfo->ipAddr[i].port;
@@ -539,14 +542,18 @@ static char *doSerializeTableInfo(SQueryTableMsg* pQueryMsg, SSqlObj *pSql, char
       int32_t index = pTableMetaInfo->vgroupIndex;
       assert(index >= 0);
   
-      pVgroupInfo = &pTableMetaInfo->vgroupList->vgroups[index];
+      if (pTableMetaInfo->vgroupList->numOfVgroups > 0) {
+        pVgroupInfo = &pTableMetaInfo->vgroupList->vgroups[index];
+      }
       tscDebug("%p query on stable, vgIndex:%d, numOfVgroups:%d", pSql, index, pTableMetaInfo->vgroupList->numOfVgroups);
     } else {
       pVgroupInfo = &pTableMeta->vgroupInfo;
     }
 
     tscSetDnodeIpList(pSql, pVgroupInfo);
-    pQueryMsg->head.vgId = htonl(pVgroupInfo->vgId);
+    if (pVgroupInfo != NULL) {
+      pQueryMsg->head.vgId = htonl(pVgroupInfo->vgId);
+    }
 
     STableIdInfo *pTableIdInfo = (STableIdInfo *)pMsg;
     pTableIdInfo->tid = htonl(pTableMeta->sid);