fix(tsdb): fix invalid ptr.

source/dnode/vnode/src/tsdb/tsdbRead2.c

@@ -5818,6 +5818,7 @@ void tsdbUntakeReadSnap2(STsdbReader* pReader, STsdbReadSnap* pSnap, bool proact
 void tsdbReaderSetId2(STsdbReader* pReader, const char* idstr) {
   taosMemoryFreeClear(pReader->idStr);
   pReader->idStr = taosStrdup(idstr);
+  pReader->status.fileIter.pLastBlockReader->mergeTree.idStr = pReader->idStr;
 }
 
 void tsdbReaderSetCloseFlag2(STsdbReader* pReader) { pReader->code = TSDB_CODE_TSC_QUERY_CANCELLED; }