fixing window binding

src/main/java/com/unicenta/pos/payment/PaymentGatewayPaymentSense.java

@@ -36,7 +36,7 @@ public class PaymentGatewayPaymentSense implements PaymentGateway {
 
     Window getPaymentWindow() {
         for (Window window : Window.getWindows()) {
-            if (window.isActive()) {
+            if (window instanceof JPaymentSelectReceipt) {
                 return window;
             }
         }

src/main/java/com/unicenta/pos/payment/PaymentGatewayTeya.java

@@ -35,7 +35,7 @@ public class PaymentGatewayTeya implements PaymentGateway {
 
     Window getPaymentWindow() {
         for (Window window : Window.getWindows()) {
-            if (window.isActive()) {
+            if (window instanceof JPaymentSelectReceipt) {
                 return window;
             }
         }