FINERACT-2015: Fix saving account with withdrawal fee

[SamaSVM]

Description

Fix NullPointerException in SavingsAccount.payWithdrawalFee() when performing account transfers with withdrawal fee enabled. During account transfers, paymentDetail is null because transfers don't use a payment type, but the code unconditionally called paymentDetail.getPaymentType().getName() causing the transaction to fail.

Checklist

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[IOhacker]

@SamaSVM There's a new ci action for PRs to check that new commits are signed.

All committers already have PGP/GPG keys, so just make sure you're also signing commits. You can add this to your ~/.gitconfig (or equivalent) to do it automatically:

[commit]
gpgSign = true

Upload your public key to github to make the verified badges green.

More info: FINERACT-2177, PR #5431.

Hints: 1) try it locally before pushing. 2) have git run it for you: Create .git/hooks/pre-push with:

#!/bin/sh
scripts/verify-signed-commits.sh --strict

Be sure to make that script executable.