title: php : add Contact to List mailjet V3 simple Api
body: <p>I try to add a contact to a list of contact in my Mailjet account, there is my code :</p>
  
  <pre><code>&lt;?php
  
  require('../mailjet_apiv3/src/Mailjet/php-mailjet-v3-simple.class.php');
  
  $mj = new Mailjet($apiKey, $secretKey);
  $list_id =123;
  $params = array(
      'method'    =&gt; 'POST',
      'Email' =&gt;  'test@tst.tst'
  );
              $result = $mj-&gt;contact($params);
  
              if(isset($result-&gt;StatusCode) &amp;&amp; $result-&gt;StatusCode == '400')
                  return false;
  
              $contact_id = $result-&gt;Data[0]-&gt;ID;
  
              // Add the contact to a contact list
              $params = array(
                  'method'    =&gt; 'POST',
                  'ContactID' =&gt; $contact_id,
                  'ListID'    =&gt; $list_id
              );
              $result = $mj-&gt;listrecipient($params);
  ?&gt;
  </code></pre>
  
  <p>I get this error : 
  Notice: Trying to get property of non-object in .../addContactMailJet.php on line 30.</p>
  
  <p>I could not find the problem, have someone idea what is wrong !</p>