title: Multi get returns source as null after bulk update
body: <p>I am using elastic search multi get for reading documents after bulk update. Its returning some document sources as null. </p>
  
  <pre><code> MultiGetRequestBuilder builder = client.prepareMultiGet();
  
   builder.setRefresh(true);
  
   builder.add(indexName, type, idsList);
  
   MultiGetResponse multiResponse = builder.execute().actionGet();
  
   for (MultiGetItemResponse response : multiResponse.getResponses())
   {
           String customerJson = response.getResponse().getSourceAsString();
           System.out.println("customerJson::" + customerJson);
   }
  </code></pre>
  
  <p>Any issues in my code? Thanks in advance.</p>