How to test the existence of a file in a webform email twig template

Hi, I have a webform with a Document File field. In my twig email template, I want to test if that field is empty. For text area fields for example, this syntax works :

{% if webform_token('[webform_submission:values:question_text_area:value]', webform_submission) %}
 <br>
 <table>
  <tr>
  <th>Questions</th>
  </tr>
  <tr>
   <td>{{ webform_token('[webform_submission:values:question_text_area:value]', webform_submission) }}</td>
  </tr>
 </table>
 {% endif %}

But for a Document File field, the same syntax does not work, meaning that if no file is uploaded, that part of my template is still printed.

I tried 

{% if webform_token('[webform_submission:values:joindre_fichiers:value]', webform_submission) %}

or 

{% if webform_token('[webform_submission:values:joindre_fichiers:value]', webform_submission) is not null %}

or 

{% if webform_token('[webform_submission:values:joindre_fichiers]', webform_submission) is not null %}

and none of them work.

Does anybody know the proper syntax for what I’m trying to do? Thanks!

Drupal version: 


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