Admin | Customers edit customer undefined key when customer fax turned off

zc157d vanilla with PHP 8.0

Minor bug
Warning Undefined array key "customers_fax" in admin\customers.php on line 92.

This occurs when Admin | Configuration | Customer Details | Fax Number = false
and Customer Details are edited.

I changed (changes in red)

Code:

---

$customers_fax = zen_db_prepare_input($_POST['customers_fax'] );

---

to

Code:

---

$customers_fax = zen_db_prepare_input(($_POST['customers_fax'] ?? ''));

---

Most of these things have already been dealt with on Github, always worth having a search in the issues there first:
https://github.com/zencart/zencart/pull/3618