Warning: Undefined array key "override" in EmailBuilderManager.php).

Hi,

Thank you for this module. I've been using them for a long time. However, after upgrading from version '1.2.1' to '1.4.0', I have been receiving an error on admin/config/development/performance (after clearing the cache).

Warning: Undefined array key "override" in Drupal\symfony_mailer\Processor\EmailBuilderManager->processDefinition() (line 97 of modules/contrib/symfony_mailer/src/Processor/EmailBuilderManager.php).
Drupal\symfony_mailer\Processor\EmailBuilderManager->processDefinition(Array, 'adpomail') (Line: 287)
Drupal\Core\Plugin\DefaultPluginManager->findDefinitions() (Line: 204)
Drupal\symfony_mailer\Processor\EmailBuilderManager->findDefinitions() (Line: 175)
Drupal\Core\Plugin\DefaultPluginManager->getDefinitions() (Line: 92)
Drupal\symfony_mailer\Processor\MailerConfigOverride->buildCache() (Line: 52)
Drupal\symfony_mailer\Processor\MailerConfigOverride->loadOverrides(Array) (Line: 209)
Drupal\Core\Config\ConfigFactory->loadOverrides(Array) (Line: 169)
Drupal\Core\Config\ConfigFactory->doLoadMultiple(Array, 1) (Line: 104)
Drupal\Core\Config\ConfigFactory->doGet('core.extension') (Line: 89)
Drupal\Core\Config\ConfigFactory->get('core.extension') (Line: 70)
Drupal\Core\Extension\ThemeHandler->listInfo() (Line: 169)
block_rebuild()
call_user_func_array(Object, Array) (Line: 426)
Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object, 'block') (Line: 405)
Drupal\Core\Extension\ModuleHandler->invokeAllWith('rebuild', Object) (Line: 433)
Drupal\Core\Extension\ModuleHandler->invokeAll('rebuild') (Line: 579)
drupal_flush_all_caches() (Line: 192)
Drupal\system\Form\PerformanceForm->submitCacheClear(Array, Object)
call_user_func_array(Array, Array) (Line: 114)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object) (Line: 52)
Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object) (Line: 592)
Drupal\Core\Form\FormBuilder->processForm('system_performance_settings', Array, Object) (Line: 320)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 564)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 169)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)
Warning: Undefined array key "override" in Drupal\symfony_mailer\Processor\EmailBuilderManager->Drupal\symfony_mailer\Processor\{closure}() (line 215 of modules/contrib/symfony_mailer/src/Processor/EmailBuilderManager.php).
Drupal\symfony_mailer\Processor\EmailBuilderManager->Drupal\symfony_mailer\Processor\{closure}(Array)
array_filter(Array, Object) (Line: 216)
Drupal\symfony_mailer\Processor\EmailBuilderManager->findDefinitions() (Line: 175)
Drupal\Core\Plugin\DefaultPluginManager->getDefinitions() (Line: 92)
Drupal\symfony_mailer\Processor\MailerConfigOverride->buildCache() (Line: 52)
Drupal\symfony_mailer\Processor\MailerConfigOverride->loadOverrides(Array) (Line: 209)
Drupal\Core\Config\ConfigFactory->loadOverrides(Array) (Line: 169)
Drupal\Core\Config\ConfigFactory->doLoadMultiple(Array, 1) (Line: 104)
Drupal\Core\Config\ConfigFactory->doGet('core.extension') (Line: 89)
Drupal\Core\Config\ConfigFactory->get('core.extension') (Line: 70)
Drupal\Core\Extension\ThemeHandler->listInfo() (Line: 169)
block_rebuild()
call_user_func_array(Object, Array) (Line: 426)
Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object, 'block') (Line: 405)
Drupal\Core\Extension\ModuleHandler->invokeAllWith('rebuild', Object) (Line: 433)
Drupal\Core\Extension\ModuleHandler->invokeAll('rebuild') (Line: 579)
drupal_flush_all_caches() (Line: 192)
Drupal\system\Form\PerformanceForm->submitCacheClear(Array, Object)
call_user_func_array(Array, Array) (Line: 114)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object) (Line: 52)
Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object) (Line: 592)
Drupal\Core\Form\FormBuilder->processForm('system_performance_settings', Array, Object) (Line: 320)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 564)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 169)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Please note that there is noting special on line 287 in my custom module (just a comment // send admin email)

        $mail_service = \Drupal::service('plugin.manager.mail');

        // send admin email
        $config = \Drupal::config('admin_general_settings.settings');
        $proforma_emails = $config->get('proforma_emails');
        $proforma_emails_array = explode("\r\n", $proforma_emails);

        // $mail_admin_service = \Drupal::service('adpomail.mail_proforma');
        // $mail_admin_service->sendMail($params);
        $params = [
          'subject' => t('New Proforma Order - @number', ['@number' => $order_id]),
          'from' => $site_mail,
          'uid' => $uid,
          'order_id' => $order_id,
          'payment_gateway_label' =>  $entity->payment_gateway->first()->entity->label()
        ];
        $mail_service->mail(
          'adpomail', 
          'proforma_admin',
          $proforma_emails_array,
          $account->getPreferredLangcode(),
          $params,
          $site_mail,
          true
        );

I can only presume that some configurations were not imported during the update (I was using Symfony Mailer BC).