LNURLw cannot be reused after a failed withdrawal attempt

[thespielplatz]

Versions:

• LNbits version: 0.12.2
• lnurlw: 0.1.5

Description:
When a withdrawal via LNURLw fails, the withdrawal count (used) in the UI increments, preventing the same LNURLw from being reused. This issue can be reproduced, if the failure is instantaneous e.g.when a payment is rejected because it originates from the same LND node (self-payments are in some cases not allowed by LND).

Steps to Reproduce:

• Create a new LNURLw with a limit of one withdrawal.
• Attempt to make a withdrawal by sending an invoice from the same LND node back to the LNURLw callback for payment.
• Observe that the payment fails immediately with the error self-payments not allowed (by LND)
• Note that the withdrawal count has incremented, and the LNURLw can no longer be reused.

Expected Behavior:
If a payment fails instantly (e.g., due to self-payments not allowed), the withdrawal count should decrease again and the same LNURLw should be available for reuse.

Additional Consideration:
Optionally, if a payment remains pending and is later invalidated, it would be beneficial if the same LNURLw could be reused in these scenarios as well.