title: How to get rid of "null" node in payload (fulfillment response)?
body: <p>I'm using <code>dialogflow-fulfillment</code> for fulfillment. I am trying to send a payload using the following function;</p>
  
  <pre><code>function getName(agent) {
          let options = {
            "options": [
                  {
                      "id": "make_reservation",
                      "text": "Reservations",
                      "payload": "make_reservation"
                    }
              ]
          };
  
          let newPayload = new Payload('PLATFORM_UNSPECIFIED', options);
          agent.add('added by webhook');
          agent.add(newPayload);
  }
  </code></pre>
  
  <p>But I'm getting a <code>null</code> node in the fulfillment response. </p>
  
  <pre><code>{
    "payload": {
      "null": {
        "options": [
          {
            "id": "make_reservation",
            "text": "Reservations",
            "payload": "make_reservation"
          }
        ]
      }
    },
    "outputContexts": []
  }
  </code></pre>
  
  <p>In the place of the  <code>null</code> node, I need the <code>options</code> node. Any idea how to do that?</p>
  
  <p>Thanks</p>