Fix race condition in BTC sent confirmation popup

[ghost]

Fixes #5331, Fixes #5305

There is a race condition with the BTC display of the sent confirmation popup. The address field and senders amount were obtained from GUI input elements which are cleared after a transaction has been sent. So the fields could be empty when the confirmation popup is shown after the wallet calls back with success.

Solution is to move a variable sendersAmount from class scope to method scope and make it final. Likewise the withdrawToAddress must be defined in method scope so that the method does not access the GUI input field after it has been cleared.

The problem does not occur for displaying BSQ sent transactions, because the relevant parameters are already method-scoped and immutable.

---

Testing

The issue can be reproduced consistently if you introduce a delay of 1 second in the processing of the wallet OnSuccess callback.

// testing fix for #5331 [delay the async popup by 1 sec]
UserThread.runAfter(() -> {
    new TxDetails(transaction.getTxId().toString(), withdrawToAddress, formatter.formatCoinWithCode(sendersAmount))
            .dontShowAgainId(key)
            .show();
}, 1, TimeUnit.SECONDS);

It helps verify that the fix works correctly. (The delay was for testing/verification only, not included in PR).

[ghost]

Tested & ready for review.

[ripcurlx]

ACK - Tested it on Regtest

Before

After