[BUG] Stripe invoice.upcoming webhooks with null next_payment_attempt cause TypeError

[mguidetti]

Bug Report

Describe the Bug:

The next_payment_attempt attribute of Stripe's Invoice object is nullable for invoices where collection_method=send_invoice

If an invoice.upcoming webhook with a null next_payment_attempt attribute is received by Pay, Pay::Stripe::Webhooks::SubscriptionRenewing will raise a TypeError can't convert NilClass into an exact number because Time.zone.at cannot receive null arguments

pay/lib/pay/stripe/webhooks/subscription_renewing.rb

Line 21 in 5b9a107

date: Time.zone.at(event.data.object.next_payment_attempt)

To Reproduce:

1. Receive a Stripe invoice.upcoming webhook with a null next_payment_attempt attribute

Expected Behavior:
The webhook should successfully process and send an subscription renewing email.

Actual Behavior:
TypeError can't convert NilClass into an exact number is raised

Environment:

• Pay gem version: 8.3.0
• Ruby version: 3.3.6
• Rails version: 7.2
• Operating System: Ubuntu 24

Possible Fix:
The next_payment_attempt can be safe navigated to handle null values and solve this error, but the subscription renewing email should probably be modified to handle conditions where next_payment_attempt is not set.

Labels to Apply:
bug

Checklist:

• I have searched for similar issues and couldn't find any
• I have checked the documentation for relevant information
• I have included all the required information