Undefined array key "VALUE"

[fglueck]

Guidelines

• I understand that if I fail to adhere to contribution guidelines and/or fail to provide all required details, this issue may be closed without review.

Description of the bug

If an SELECT-OPTION have no value attribute, there will throw:
Undefined array key "VALUE"

/srv/www/html/cockpit/inc/vendor/mpdf/mpdf/src/Tag/Option.php
Line: 30

Sample:

mPDF version

current

PHP Version and environment (server type, cli provider etc., enclosing libraries and their respective versions)

PHP 8.0 + 8.3

Reproducible PHP+CSS+HTML snippet suffering by the error

  <select id="contact" style="width: 130px" data-mail_body="..."  data-subject=".." onchange="/* */">
  <option selected="true" disabled="disabled">@ Mailanfrage zu:</option>
  <option value="..."         data-subject="Kaufvertragsdaten"            data-body_add="">Kaufvertragsdaten</option>
  </select>

[finwe]

This already has a fix here #1934 which I have forgotten about. Will revisit.