title: Missing '$template' parameter on emails
body: <p>I'm trying to send an email after our IPN sends payment status updates, and email customers as well.  I have the following code</p>
  
  <pre><code>$file_attachement = null; 
  Mail::Send( (int)$email_order-&gt;id_lang, 
  'order_conf', 
  Mail::l('Order confirmation', (int)$email_order-&gt;id_lang), 
  null, 
  $email_customer-&gt;email, 
  $email_customer-&gt;firstname.' '.$email_customer-&gt;lastname, 
  null, 
  null, 
  $file_attachement, 
  null, 
  _PS_MAIL_DIR_, false, (int)$email_order-&gt;id_shop );
  </code></pre>
  
  <p>And I get the following error</p>
  
  <pre><code>Missing '$template' parameter...smarty_internal_templatebase.php on line 177
  </code></pre>
  
  <p>The <code>order_conf</code> exists, and I can look at the <code>Advanced Parameters-&gt;Email</code> and see that its trying to send.</p>
  
  <p>Prestashop Version is 1.7.5.1</p>