title: DynamoDB mapper.batchLoad nullPointerException
body: <p>I'm getting a nullPointerException in DynamoDB mapper.batchLoad. This is the code:</p>
  
  <pre><code>    DynamoDBMapper mapper = new DynamoDBMapper(dynamoDB);
      ArrayList&lt;Object&gt; itemsToGet = new ArrayList&lt;&gt;();
  
      Post post = new Post();
      post.setCode("001");
      post.setNick("myNick");
      itemsToGet.add(post);
  
      Map&lt;String, List&lt;Object&gt;&gt; items = mapper.batchLoad(itemsToGet);
  </code></pre>
  
  <p>And return this error:</p>
  
  <pre><code>06-04 16:32:20.108 11533-11576/com.resurgence.photofusion E/AndroidRuntime: FATAL EXCEPTION: pool-1-thread-1
                                                                          Process: com.resurgence.photofusion, PID: 11533
                                                                          java.lang.NullPointerException: Attempt to invoke interface method 'com.amazonaws.services.dynamodbv2.model.BatchGetItemResult com.amazonaws.services.dynamodbv2.AmazonDynamoDB.batchGetItem(com.amazonaws.services.dynamodbv2.model.BatchGetItemRequest)' on a null object reference
                                                                              at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.processBatchGetRequest(DynamoDBMapper.java:1870)
                                                                              at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.batchLoad(DynamoDBMapper.java:1781)
                                                                              at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.batchLoad(DynamoDBMapper.java:1835)
                                                                              at com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBMapper.batchLoad(DynamoDBMapper.java:1801)
                                                                              at com.resurgence.photofusion.database.PostsCrud.selectPostsByFeeds(PostsCrud.java:106)
                                                                              at com.resurgence.photofusion.activities.MainActivity$1.run(MainActivity.java:181)
                                                                              at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
                                                                              at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
                                                                              at java.lang.Thread.run(Thread.java:818)
  </code></pre>
  
  <p>'Code' and 'Nick' are hashkey and rangekey of 'Posts' table and I'm trying to follow this example:</p>
  
  <p><a href="http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.Methods.html#d0e32065" rel="nofollow">http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.Methods.html#d0e32065</a></p>
  
  <p>I'm using batchLoad incorrectly? Could anyone help me?
  Thanks in advance.</p>