Do not display confirmation icon for 0 BTC tx

If we do not get any BTC from a mediated payout tx we do not know about
the confirmation state so it would stay always in the unconfirmed state.
To avoid that confusion we prefer to hide the icon. This is a known
issue from BitcoinJ but we have not found a solution for that yet.

desktop/src/main/java/bisq/desktop/main/funds/transactions/TransactionsListItem.java

@@ -223,6 +223,10 @@ public void onTransactionConfidenceChanged(TransactionConfidence confidence) {
                     } else if (trade.getPayoutTx() != null &&
                             trade.getPayoutTx().getHashAsString().equals(txId)) {
                         details = Res.get("funds.tx.multiSigPayout", tradeId);
+
+                        if (amountAsCoin.isZero()) {
+                            txConfidenceIndicator.setVisible(false);
+                        }
                     } else {
                         Trade.DisputeState disputeState = trade.getDisputeState();
                         if (disputeState == Trade.DisputeState.DISPUTE_CLOSED) {