Log errors if payment processor cannot be found for IPN

CRM/Core/Payment/MJWIPNTrait.php

@@ -94,8 +94,10 @@ trait CRM_Core_Payment_MJWIPNTrait {
    * @throws \Civi\Payment\Exception\PaymentProcessorException
    */
   protected function getPaymentProcessor() {
-    $paymentProcessorID = CRM_Utils_Request::retrieveValue('processor_id', 'Positive', NULL, TRUE, 'GET');
-
+   $paymentProcessorID = CRM_Utils_Request::retrieveValue('processor_id', 'Positive', NULL, FALSE, 'GET');
+   if (!$paymentProcessorID) {
+     $this->exception('Failed to get payment processor ID');
+   }
     try {
       $this->_paymentProcessor = \Civi\Payment\System::singleton()->getById($paymentProcessorID);
     }
@@ -399,8 +401,9 @@ trait CRM_Core_Payment_MJWIPNTrait {
    * @throws \Civi\Payment\Exception\PaymentProcessorException
    */
   protected function exception($message) {
-    $errorMessage = $this->_paymentProcessor->getPaymentProcessorLabel() . ' Exception: Event: ' . $this->eventType . ' Error: ' . $message;
-    Civi::log()->debug($errorMessage);
+    $label = method_exists($this->_paymentProcessor, 'getPaymentProcessorLabel') ? $this->_paymentProcessor->getPaymentProcessorLabel() : __CLASS__;
+    $errorMessage = $label . ' Exception: Event: ' . $this->eventType . ' Error: ' . $message;
+    Civi::log()->error($errorMessage);
     if ($this->exitOnException) {
       http_response_code(400);
       exit(1);