fix function signature to match interface & not give warning

CRM/Core/Payment/PayJunction.php

@@ -53,7 +53,7 @@ class CRM_Core_Payment_PayJunction extends CRM_Core_Payment {
    * @static
    *
    */
-  static function &singleton($mode, &$paymentProcessor) {
+  static function &singleton($mode, &$paymentProcessor, &$paymentForm = NULL, $force = false) {
     $processorName = $paymentProcessor['name'];
     if (self::$_singleton[$processorName] === NULL) {
       self::$_singleton[$processorName] = new CRM_Core_Payment_PayJunction($mode, $paymentProcessor);