[TS-2016](query,insert,other,connector,tools):fix app error of select from...

[TS-2016](query,insert,other,connector,tools):fix app error of select from (select * from empty_stable) by set subquery command to retrieve empty results

src/client/src/tscUtil.c

@@ -4223,7 +4223,11 @@ void executeQuery(SSqlObj* pSql, SQueryInfo* pQueryInfo) {
       pSql->pSubs[i] = pNew;
 
       SSqlCmd* pCmd = &pNew->cmd;
-      pCmd->command = TSDB_SQL_SELECT;
+      if (pSub->command == TSDB_SQL_RETRIEVE_EMPTY_RESULT) {
+        pCmd->command = TSDB_SQL_RETRIEVE_EMPTY_RESULT;
+      } else {
+        pCmd->command = TSDB_SQL_SELECT;
+      }
       if ((code = tscAddQueryInfo(pCmd)) != TSDB_CODE_SUCCESS) {
         goto _error;
       }