title: Get RealmObject attribute asynchronously
body: <p>I have a conversation RealmObject which contains a RealmList of messages (My messages don't know about the conversations). I want to query and sort them asynchronously.<br>
  Here is my awful attempt but I post it to give you a better idea of ​what I want to do : </p>
  
  <pre><code>return realm.where(Conversation.class)
              .equalTo("id",conversationId)
              .findFirstAsync()
              .getMessages().sort("receivedDate", Sort.DESCENDING)
              .asFlowable();
  </code></pre>
  
  <p>It doesn't work and this exception has been thrown:  </p>
  
  <blockquote>
    <p>java.lang.IllegalStateException: The pending query has not been executed</p>
  </blockquote>
  
  <p>Currently I have no idea how to query them asynchronously and get back them in the UI thread without changing my schema.</p>
  
  <p><strong>Edit:</strong><br>
  My schema is very simple :</p>
  
  <pre><code>public class Message extends RealmObject{
  private String content;
  private Date receivedDate;
  }
  
  public class Conversation extends RealmObject{
      private String id;
      private RealmList&lt;Message&gt; messages;
  }
  </code></pre>