Issue #2936642 by tim.plunkett: Getting runtime contexts will generate an...

Issue #2936642 by tim.plunkett: Getting runtime contexts will generate an E_WARNING for anonymous users

core/modules/user/src/ContextProvider/CurrentUserContext.php

@@ -50,9 +50,11 @@ public function __construct(AccountInterface $account, EntityManagerInterface $e
   public function getRuntimeContexts(array $unqualified_context_ids) {
     $current_user = $this->userStorage->load($this->account->id());
 
-    // @todo Do not validate protected fields to avoid bug in TypedData, remove
-    //   this in https://www.drupal.org/project/drupal/issues/2934192.
-    $current_user->_skipProtectedUserFieldConstraint = TRUE;
+    if ($current_user) {
+      // @todo Do not validate protected fields to avoid bug in TypedData,
+      //   remove this in https://www.drupal.org/project/drupal/issues/2934192.
+      $current_user->_skipProtectedUserFieldConstraint = TRUE;
+    }
 
     $context = new Context(new ContextDefinition('entity:user', $this->t('Current user')), $current_user);
     $cacheability = new CacheableMetadata();