[td-225] fix a memory leak in query.

src/tsdb/src/tsdbRead.c

@@ -2085,6 +2085,8 @@ STimeWindow changeTableGroupByLastrow(STableGroupInfo *groupList) {
       totalNumOfTable++;
       taosArrayPush(pGroup, &keyInfo);
     } else {
+      taosArrayDestroy(pGroup);
+
       taosArrayRemove(groupList->pGroupList, j);
       numOfGroups -= 1;
       j -= 1;