[Bug]: Pay to LN zero amount invoice broken

[aldertnl]

Describe the bug

Paying to a zero amount LN invoice is currently broken.

This is problematic, as copying and sharing a BIP21 URI with BOLT 11 invoice (with both on-chain address and Lightning invoice) is the default behavior in the receive flow, and thus users can currently only use LN receive functionality if they specify an invoice.

Reproduce

1. Go to 'Receive'
2. Click on 'Copy'
3. Share invoice with someone
4. They try to pay the invoice
5. It will not work

Screenshots / Recording

No response

Operating system

iPhone (and probably Android)

Bitkit version

1.0 (19)

Log output

Error creating transaction