fix(query): handle the case of the single block in last files.

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

@@ -324,6 +324,14 @@ int32_t tLDataIterOpen(struct SLDataIter **pIter, SDataFReader *pReader, int32_t
         taosArrayDestroy(pBlockLoadInfo->aSttBlk);
         pBlockLoadInfo->aSttBlk = pTmp;
       }
+    } else {  // size == 1
+      SSttBlk *pStart = taosArrayGet(pBlockLoadInfo->aSttBlk, 0);
+      if (pStart->suid != suid) {
+        (*pIter)->iSttBlk = -1;
+        double el = (taosGetTimestampUs() - st) / 1000.0;
+        tsdbDebug("load the last file info completed, elapsed time:%.2fms, %s", el, idStr);
+        return code;
+      }
     }
 
     double el = (taosGetTimestampUs() - st) / 1000.0;