fix file corrupt

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

@@ -557,6 +557,7 @@ int32_t tsdbReadBlockIdx(SDataFReader *pReader, SArray *aBlockIdx, uint8_t **ppB
   }
 
   // decode
+  n = 0;
   n = tGetU32(*ppBuf + n, &delimiter);
   ASSERT(delimiter == TSDB_FILE_DLMT);
 
@@ -1285,6 +1286,7 @@ int32_t tsdbWriteBlockIdx(SDataFWriter *pWriter, SArray *aBlockIdx, uint8_t **pp
   if (code) goto _err;
 
   // build
+  n = 0;
   n = tPutU32(*ppBuf + n, TSDB_FILE_DLMT);
   for (int32_t iBlockIdx = 0; iBlockIdx < taosArrayGetSize(aBlockIdx); iBlockIdx++) {
     n += tPutBlockIdx(*ppBuf + n, taosArrayGet(aBlockIdx, iBlockIdx));