Can't create invoices

[rdoursenaud]

Bug

Can't create subscription with invoice without payment.

Invoice creation fails silently.

Debugging the code:

$result=$invoice->create($user);

complains about date_pointoftax not being in the correct format.

Introduced by @eldy on 3ddf427

Environment

• Version: Develop
• URL: adherents/card_subscriptions.php?rowid=1&action=addsubscription

Expected and actual behavior

Create an invoice!
(And/or display an error message)

Steps to reproduce the behavior

Enable members and customer invoice modules.
Link a member to a thirdparty.
Create a subscription with invoice for this member.

[rdoursenaud]

It's worse. Can't create any invoice at all.