Issue #3311032 by jrockowitz: Webform hook may pass null webform instance, leading to error

webform.api.php

@@ -442,12 +442,13 @@ function hook_webform_third_party_settings_form_alter(array &$form, \Drupal\Core
  * @see \Drupal\webform\Plugin\WebformHandlerInterface
  */
 function hook_webform_handler_invoke_alter(\Drupal\webform\Plugin\WebformHandlerInterface $handler, $method_name, array &$args) {
-  $webform = $handler->getWebform();
-  $webform_submission = $handler->getWebformSubmission();
-
-  $webform_id = $handler->getWebform()->id();
   $handler_id = $handler->getHandlerId();
-  $state = $webform_submission->getState();
+  $webform = $handler->getWebform();
+  if ($webform) {
+    $webform_id = $handler->getWebform()->id();
+    $webform_submission = $handler->getWebformSubmission();
+    $state = $webform_submission->getState();
+  }
 }
 
 /**