diff --git a/core/modules/hal/src/Normalizer/EntityReferenceItemNormalizer.php b/core/modules/hal/src/Normalizer/EntityReferenceItemNormalizer.php
index 48dbb81b47..a0b5b89a20 100644
--- a/core/modules/hal/src/Normalizer/EntityReferenceItemNormalizer.php
+++ b/core/modules/hal/src/Normalizer/EntityReferenceItemNormalizer.php
@@ -82,10 +82,10 @@ public function normalize($field_item, $format = NULL, array $context = []) {
 
     // Normalize the target entity.
     $embedded = $this->serializer->normalize($target_entity, $format, $context);
-    $link = $embedded['_links']['self'];
     // If the field is translatable, add the langcode to the link relation
     // object. This does not indicate the language of the target entity.
-    if ($langcode) {
+    $link = $embedded['_links']['self'] ?? NULL;
+    if ($link && $langcode) {
       $embedded['lang'] = $link['lang'] = $langcode;
     }
 
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index 9a8d8c999c..b44430c7fc 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -648,7 +648,7 @@ function template_preprocess_node(&$variables) {
     unset($variables['elements']['uid']);
   }
 
-  if (!$skip_custom_preprocessing || !$node->getFieldDefinition('title')->isDisplayConfigurable('view')) {
+  if (isset($variables['elements']['title']) && (!$skip_custom_preprocessing || !$node->getFieldDefinition('title')->isDisplayConfigurable('view'))) {
     $variables['label'] = $variables['elements']['title'];
     unset($variables['elements']['title']);
   }
diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index 6dced6adab..d09886bcbb 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -495,7 +495,7 @@ function rdf_preprocess_comment(&$variables) {
   }
   // Adds RDFa markup for the date of the comment.
   $created_mapping = $mapping->getPreparedFieldMapping('created');
-  if (!empty($created_mapping)) {
+  if (!empty($created_mapping) && isset($comment->rdf_data)) {
     // The comment date is precomputed as part of the rdf_data so that it can be
     // cached as part of the entity.
     $date_attributes = $comment->rdf_data['date'];