diff --git a/core/lib/Drupal/Core/Entity/EntityNG.php b/core/lib/Drupal/Core/Entity/EntityNG.php
index 00f546e..c74c9d5 100644
--- a/core/lib/Drupal/Core/Entity/EntityNG.php
+++ b/core/lib/Drupal/Core/Entity/EntityNG.php
@@ -383,7 +383,7 @@ public function updateOriginalValues() {
     foreach ($this->getPropertyDefinitions() as $name => $definition) {
       if (empty($definition['computed']) && !empty($this->fields[$name])) {
         foreach ($this->fields[$name] as $langcode => $field) {
-          $field->cleanValue();
+          $field->filterEmptyValues();
           $this->values[$name][$langcode] = $field->getValue();
         }
       }
diff --git a/core/lib/Drupal/Core/Entity/Field/FieldInterface.php b/core/lib/Drupal/Core/Entity/Field/FieldInterface.php
index 63b6dd0..dc05036 100644
--- a/core/lib/Drupal/Core/Entity/Field/FieldInterface.php
+++ b/core/lib/Drupal/Core/Entity/Field/FieldInterface.php
@@ -28,11 +28,9 @@
 interface FieldInterface extends ListInterface, AccessibleInterface {
 
   /**
-   * Cleans the field value.
-   *
-   * Removes empty field items and re-numbers the item deltas.
+   * Filters out empty field items and re-numbers the item deltas.
    */
-  public function cleanValue();
+  public function filterEmptyValues();
 
   /**
    * Gets a property object from the first field item.
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/Field.php b/core/lib/Drupal/Core/Entity/Field/Type/Field.php
index 50cd51d..618da1c 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/Field.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/Field.php
@@ -51,14 +51,11 @@ public function __construct(array $definition, $name = NULL, TypedDataInterface
   /**
    * {@inheritdoc}
    */
-  public function cleanValue() {
+  public function filterEmptyValues() {
     if (isset($this->list)) {
-      foreach ($this->list as $delta => $item) {
-        if ($item->isEmpty()) {
-          unset($this->list[$delta]);
-        }
-      }
-      $this->list = array_values($this->list);
+      $this->list = array_values(array_filter($this->list, function($item) {
+        return !$item->isEmpty();
+      }));
     }
   }
 
diff --git a/core/modules/forum/forum.module b/core/modules/forum/forum.module
index af1330e..04c454a 100644
--- a/core/modules/forum/forum.module
+++ b/core/modules/forum/forum.module
@@ -332,7 +332,7 @@ function forum_node_presave(EntityInterface $node) {
     $node->icon = !empty($node->icon) ? $node->icon : '';
     reset($node->taxonomy_forums);
     $langcode = key($node->taxonomy_forums);
-    if (!empty($node->taxonomy_forums[$langcode])) {
+    if (!empty($node->taxonomy_forums[$langcode]) && !$node->isNew()) {
       $node->forum_tid = $node->taxonomy_forums[$langcode][0]['tid'];
       $old_tid = db_query_range("SELECT f.tid FROM {forum} f INNER JOIN {node} n ON f.vid = n.vid WHERE n.nid = :nid ORDER BY f.vid DESC", 0, 1, array(':nid' => $node->nid))->fetchField();
       if ($old_tid && isset($node->forum_tid) && ($node->forum_tid != $old_tid) && !empty($node->shadow)) {