Bug in Payplans renewal when an invoice has been refunded

Hi

I have debugged an issue in Payplans 4.2.2 that causes me some trouble with users renewal of their subscription. I have reproduced this independantly on my live site, so you can too.

It goes as like this:

- User purchased a sub in November 2018
- They renew in November 2019 (Paypal) but there's a problem somewhere and they pay twice
- We refund one of the invoice. User now has one Active sub and 3 invoices: 2018, 2019 paid and 2019 refunded
- Now they want to renew in 2020: go to dashboard, hit the Renew button and they get a Fatal error:

Error: 0 call to undefined method stdClass::refresh()

I have tracked that down to /administrator/components/com_payplans/includes/renewal/renewal.php at line 71: the $invoice object is a stdClass instead of being an invoice object.
I have tracked that down then to: /administrator/components/com_payplans/includes/order/order.php at line 413.
Payplans gets the 2 invoices for that user: the oldes is active and the more recent has been redunded. Therefore at line 413

$invoice = $this->createChildInvoice($invoiceCount);

fails to create a child invoice and eventually a fatal error is triggered later on.

So there are 3 problems:

1 - This situation is not taken into account: createChildInvoice should not try to create a childInvoice from the last subscription but from the last active subscription.
2. If not possible, this should not trigger a fatal error but simply some kind of error message.

Please have a look and try fix that.

The 3rd problem is how I fix that manually until the problem is really fixed. I have tried re-creating a separate subscription expiring in a month, but when I go to the user dashboard, the "Renew" button is not displayed.

Right now, I have:

- deleted all the invoices, orders and subscriptions of that user in the database as there's no UI to delete those items
- Created a new subscription
- Set the expiration date of that subscription to November 8, 2020 (the original expiration date)

BUT: when going to the dashboard, the Renew button is not displayed. What's going on?

Please provide me for a temporary solution to allow user to renew. Why is the renew button not showing on an active subscription?

Best regards
Yannick Gaultier
weeblr.com / @weeblr