Update DirectAuthorizeRequest.php

Send empty values for state instead of null

Author: mbeech

src/Omnipay/SagePay/Message/DirectAuthorizeRequest.php

@@ -34,7 +34,7 @@ protected function getBaseAuthorizeData()
         $data['BillingAddress2'] = $card->getBillingAddress2();
         $data['BillingCity'] = $card->getBillingCity();
         $data['BillingPostCode'] = $card->getBillingPostcode();
-        $data['BillingState'] = $card->getBillingCountry() === 'US' ? $card->getBillingState() : null;
+        $data['BillingState'] = $card->getBillingCountry() === 'US' ? $card->getBillingState() : '';
         $data['BillingCountry'] = $card->getBillingCountry();
         $data['BillingPhone'] = $card->getBillingPhone();
 
@@ -45,7 +45,7 @@ protected function getBaseAuthorizeData()
         $data['DeliveryAddress2'] = $card->getShippingAddress2();
         $data['DeliveryCity'] = $card->getShippingCity();
         $data['DeliveryPostCode'] = $card->getShippingPostcode();
-        $data['DeliveryState'] = $card->getShippingCountry() === 'US' ? $card->getShippingState() : null;
+        $data['DeliveryState'] = $card->getShippingCountry() === 'US' ? $card->getShippingState() : '';
         $data['DeliveryCountry'] = $card->getShippingCountry();
         $data['DeliveryPhone'] = $card->getShippingPhone();
         $data['CustomerEMail'] = $card->getEmail();