fix remaining issue when utxo date is null

src/main/java/com/sparrowwallet/sparrow/wallet/ReceiveController.java

@@ -134,7 +134,7 @@ public class ReceiveController extends WalletFormController implements Initializ
         } else if(!currentOutputs.isEmpty()) {
             long count = currentOutputs.size();
             BlockTransactionHashIndex lastUsedReference = currentOutputs.stream().skip(count - 1).findFirst().get();
-            lastUsed.setText(lastUsedReference.getHeight() <= 0 ? "Unconfirmed Transaction" : DATE_FORMAT.format(lastUsedReference.getDate()));
+            lastUsed.setText(lastUsedReference.getHeight() <= 0 ? "Unconfirmed Transaction" : (lastUsedReference.getDate() == null ? "Unknown" : DATE_FORMAT.format(lastUsedReference.getDate())));
             lastUsed.setGraphic(getWarningGlyph());
             if(!address.getStyleClass().contains("error")) {
                 address.getStyleClass().add("error");