FIX pb with extrafield list and key '0'

Conflicts:
	htdocs/core/class/extrafields.class.php

Conflicts:
	htdocs/admin/supplier_payment.php
	htdocs/core/lib/ajax.lib.php
	htdocs/don/admin/donation.php
	htdocs/product/admin/product.php

Fix: "scandir" in url is blocked in some providers

Conflicts:
	scripts/cron/cron_run_jobs.php

FIX 'Error cronjob->run_job: Permission denied'

https://www.dolibarr.fr/forum/527-bugs-sur-la-version-stable-courante/59536-extrafields-commande-dans-expedition

6.0 fix