Transfer: validate destination address

including preventing two payment ids (standalone and
from integrated address)

pages/Transfer.qml

@@ -239,6 +239,19 @@ Rectangle {
         anchors.topMargin: 5
     }
 
+    function checkAddressAndPaymentID(address, payment_id, testnet) {
+      print ("testing")
+      if (!walletManager.addressValid(address, testnet))
+        return false
+      print ("address is valid")
+      var ipid = walletManager.paymentIdFromAddress(address, testnet)
+      print ("ipid: [" + ipid + "]")
+      if (ipid.length > 0)
+         return payment_id === ""
+      print ("payment_id: [" + payment_id + "]")
+      return payment_id === "" || walletManager.paymentIdValid(payment_id)
+    }
+
     StandardButton {
         id: sendButton
         anchors.left: parent.left
@@ -251,7 +264,7 @@ Rectangle {
         shadowPressedColor: "#B32D00"
         releasedColor: "#FF6C3C"
         pressedColor: "#FF4304"
-        enabled : addressLine.text.length > 0 && amountLine.text.length > 0 && (paymentIdLine.text.trim() === "" || walletManager.paymentIdValid(paymentIdLine.text.trim()))
+        enabled : amountLine.text.length > 0 && checkAddressAndPaymentID(addressLine.text.trim(), paymentIdLine.text.trim(), appWindow.persistentSettings.testnet)
         onClicked: {
             console.log("Transfer: paymentClicked")
             var priority = priorityModel.get(priorityDropdown.currentIndex).priority