Merge pull request #1450 from sangshuduo/fix-double-free-pCond

fix pCond double free issue.

src/system/detail/src/mgmtSupertableQuery.c

@@ -711,7 +711,6 @@ static int32_t mgmtFilterMeterByIndex(STabObj* pMetric, tQueryResultset* pRes, c
   // failed to build expression, no result, return immediately
   if (pExpr == NULL) {
     mError("metric:%s, no result returned, error in super table query expression:%s", pMetric->meterId, pCond);
-    tfree(pCond);
 
     return TSDB_CODE_OPS_NOT_SUPPORT;
   } else {  // query according to the binary expression