title: remote_transport_exception: When partially updating elasticsearch document using script
body: <p>I am partially updating the document using the following structure</p>
  
  <pre><code>$params = [
                  'index' =&gt; self::$currentIndex[self::INDEX_TYPE_SEARCH],
                  'type'  =&gt; self::TYPE_PRODUCT,
                  'id'    =&gt; $product_id,
                  'body'  =&gt; [
                      'script' =&gt; 'ctx._source.coupons += coupon',
                      'params' =&gt; ['coupon' =&gt; array($product_body)],
                  ]
              ];
  </code></pre>
  
  <p>However I am getting the following error: </p>
  
  <blockquote>
    <p>remote_transport_exception:
    [Gee][127.0.0.1:9300][indices:data/write/update[s]]</p>
  </blockquote>
  
  <p>Any idea if the structure is incorrect?</p>