message: Update empty stargz index.json
diff: {
  "name": "empty-file",
  "type": "reg",
  - "size": 0,
  "modtime": "2020-09-10T07:40:29Z",
  "mode": 420,
  - "offset": 0,
  "NumLink": 0,
  - "digest": "",
  - "chunkSize": 4194304
  + "digest": "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
  }
  ]
  }
  \ No newline at end of file
  