title: validate object with empty parentheses in protobuf
body: <p>I have a json file converted to protobuf format with empty parentheses in some object. Could you help me identify empty objects in protobuf (first case)? I tried to use bytes size but for a good object the size is 0 like an empty.</p>
  <p>load data</p>
  <pre><code>val json = // readFromJson
  val protobufBuilder = Converted.newBuilder()
  JsonFormat.parser.ignoringUnknownFields.merge(json, protobufBuilder)
  val converted = protobufBuilder.build()
  </code></pre>
  <ol>
  <li></li>
  </ol>
  <p>input</p>
  <pre><code>{
  “a”: 0,
  “someObject”: {}
  }
  </code></pre>
  <p>scala code</p>
  <pre><code>println(converted.hasSomeObject)  // true
  converted.getSomeObjectBytes.size() // 0
  </code></pre>
  <ol start="2">
  <li></li>
  </ol>
  <p>input</p>
  <pre><code>{
  “a”: 0,
  “someObject”: {
      “type”: 1,
      “name”: “”Jack
  }
  }
  </code></pre>
  <p>scala</p>
  <pre><code>println(converted.hasSomeObject)  // true
  converted.getSomeObjectBytes.size() // 0
  </code></pre>
  <ol start="3">
  <li></li>
  </ol>
  <p>input</p>
  <pre><code>{
  “a”: 0
  }
  </code></pre>
  <p>scala</p>
  <pre><code>println(converted.hasSomeObject)  // false
  converted.getSomeObjectBytes.size() // 0
  </code></pre>