title: ElasticsearchSinkConnector Failed to deserialize data to Avro
body: <p>I created the simplest kafka sink connector config and I'm using confluent 4.1.0:</p>
  
  <pre><code>{
    "connector.class": 
    "io.confluent.connect.elasticsearch.ElasticsearchSinkConnector",
    "type.name": "test-type",
    "tasks.max": "1",
    "topics": "dialogs",
    "name": "elasticsearch-sink",
    "key.ignore": "true",
    "connection.url": "http://localhost:9200",
    "schema.ignore": "true"
  }
  </code></pre>
  
  <p>and in the topic I save the messages in <strong>JSON</strong> </p>
  
  <pre><code>{ "topics": "resd"}
  </code></pre>
  
  <p>But in the result I get an error: </p>
  
  <blockquote>
    <p>Caused by: org.apache.kafka.common.errors.SerializationException: Error deserializing Avro message for id -1
    Caused by: org.apache.kafka.common.errors.SerializationException: Unknown magic byte!</p>
  </blockquote>