fix: last cache read problem after schema change

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

@@ -1432,6 +1432,7 @@ static int32_t mergeLast(tb_uid_t uid, STsdb *pTsdb, SArray **ppLastArray, SCach
   int16_t   nLastCol = pTSchema->numOfCols;
   int16_t   noneCol = 0;
   bool      setNoneCol = false;
+  bool      hasRow = false;
   SArray   *pColArray = NULL;
   SColVal  *pColVal = &(SColVal){0};
 
@@ -1454,6 +1455,8 @@ static int32_t mergeLast(tb_uid_t uid, STsdb *pTsdb, SArray **ppLastArray, SCach
       break;
     }
 
+    hasRow = true;
+
     code = updateTSchema(TSDBROW_SVERSION(pRow), pr, uid);
     if (TSDB_CODE_SUCCESS != code) {
       goto _err;
@@ -1545,6 +1548,9 @@ static int32_t mergeLast(tb_uid_t uid, STsdb *pTsdb, SArray **ppLastArray, SCach
   //*ppLastArray = NULL;
   // taosArrayDestroy(pColArray);
   //} else {
+  if (!hasRow) {
+    taosArrayClear(pColArray);
+  }
   *ppLastArray = pColArray;
   //}