fix: do not use non-existing method

src/QUI/Memberships/Users/MembershipUser.php

@@ -481,7 +481,8 @@ public function startAbortCancel(): void
             ]);
         }
 
-        $abortCancelUrl = Verifier::startVerification($this->getAbortCancelVerification(), true);
+        $verification = $this->createAbortCancelVerification();
+        $abortCancelUrl = $verification->getVerificationUrl();
 
         $this->setAttributes([
             'cancelStatus' => MembershipUsersHandler::CANCEL_STATUS_ABORT_CANCEL_CONFIRM_PENDING,
@@ -517,7 +518,10 @@ public function confirmAbortCancel(): void
 
         try {
             $verification = $this->getAbortCancelVerification();
-            $this->verificationRepository->delete($verification);
+
+            if ($verification) {
+                $this->verificationRepository->delete($verification);
+            }
         } catch (\Exception $Exception) {
             QUI\System\Log::writeException($Exception);
         }
@@ -595,6 +599,10 @@ public function sendConfirmCancelReminderMail(): bool
 
             $cancelVerification = $this->getCancelVerification();
 
+            if (!$cancelVerification) {
+                return false;
+            }
+
             $this->sendMail(
                 $subject,
                 dirname(__FILE__, 5) . '/templates/mail_confirmcancel_reminder.html',