prefix & suffix are received when using iron-form

[abdonrd]

When I use it in a form, the event.detail has prefix & suffix as undefined.

[samiheikki]

Tried this and cannot reproduce with current master with the following code block:

<iron-form id="form1" method="get">
      <form>
        <vaadin-text-field name="text-field">
          <div slot="prefix">$</div>
          <div slot="suffix">€</div>
        </vaadin-text-field>
        <vaadin-button onclick="form1.submit()">Submit</vaadin-button>
      </form>
    </iron-form>
    <script>
      form1.addEventListener('iron-form-submit', function(event) {
        console.log(event.detail);
      });
    </script>

event.detail: {text-field: "asd"}

[samiheikki]

Discussed with @tomivirkki and decided to close the ticket.

Issue is only reproducible if removing name attribute from a component with named slots (like vaadin-text-field) so the issue is due to iron-form.