Add handling for sagePay intolerance for empty card

Hopefully thephpleague/omnipay-sagepay#158
will be merged but for now SagePay assumes that an empty card is an ignore-everything-else-card

CRM/Core/Payment/OmnipayMultiProcessor.php

@@ -462,7 +462,7 @@ private function camelFieldName($fieldName) {
    *
    * @param array $params
    *
-   * @return array
+   * @return array|null
    */
   private function getCreditCardObjectParams($params) {
     $billingID = $locationTypes = CRM_Core_BAO_LocationType::getBilling();
@@ -516,6 +516,10 @@ private function getCreditCardObjectParams($params) {
         }
       }
     }
+    if (empty(array_filter($cardFields))) {
+      // sagepay hack - see https://github.com/thephpleague/omnipay-sagepay/issues/157#issuecomment-757448484
+      return NULL;
+    }
     return $cardFields;
   }
 
@@ -578,7 +582,9 @@ protected function getCreditCardOptions(array $params): array {
     $creditCardOptions = array_merge($creditCardOptions, $this->getProcessorPassThroughFields());
 
     CRM_Utils_Hook::alterPaymentProcessorParams($this, $params, $creditCardOptions);
-    $creditCardOptions['card'] = array_merge($creditCardOptions['card'], $this->getSensitiveCreditCardObjectOptions($params));
+    if (!empty($creditCardOptions['card'])) {
+      $creditCardOptions['card'] = array_merge($creditCardOptions['card'], $this->getSensitiveCreditCardObjectOptions($params));
+    }
     return $creditCardOptions;
   }