To reproduce:

* install python package ``pdfminer.six``
* install module attachment_indexation
* upload special attachment

BEFORE:

Error in client:

> TypeError: relatedTemporaryAttachments is not iterable

Error in logs:

> ValueError: A string literal cannot contain NUL (0x00) characters.

AFTER:

No errors

---

opw-2506038

closes odoo/odoo#70186

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>