diff -u b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/widget/AutocompleteWidgetBase.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/widget/AutocompleteWidgetBase.php
--- b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/widget/AutocompleteWidgetBase.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/widget/AutocompleteWidgetBase.php
@@ -117,6 +117,10 @@
    * Gets the entity labels.
    */
   protected function getLabels(FieldInterface $items) {
+    if ($items->isEmpty()) {
+      return array();
+    }
+
     $entity_ids = array();
     $entity_labels = array();
 
diff -u b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/widget/TestFieldWidgetMultiple.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/widget/TestFieldWidgetMultiple.php
--- b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/widget/TestFieldWidgetMultiple.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/widget/TestFieldWidgetMultiple.php
@@ -60,8 +60,8 @@
    */
   public function formElement(FieldInterface $items, $delta, array $element, $langcode, array &$form, array &$form_state) {
     $values = array();
-    foreach ($items as $delta => $value) {
-      $values[] = $value['value'];
+    foreach ($items as $delta => $item) {
+      $values[] = $item->value;
     }
     $element += array(
       '#type' => 'textfield',
diff -u b/core/modules/file/lib/Drupal/file/Plugin/field/formatter/TableFormatter.php b/core/modules/file/lib/Drupal/file/Plugin/field/formatter/TableFormatter.php
--- b/core/modules/file/lib/Drupal/file/Plugin/field/formatter/TableFormatter.php
+++ b/core/modules/file/lib/Drupal/file/Plugin/field/formatter/TableFormatter.php
@@ -32,11 +32,11 @@
   public function viewElements(EntityInterface $entity, $langcode, FieldInterface $items) {
     $elements = array();
 
-    if (!empty($items)) {
+    if (!$items->isEmpty()) {
       // Display all values in a single element.
       $elements[0] = array(
         '#theme' => 'file_formatter_table',
-        '#items' => $items,
+        '#items' => $items->getValue(TRUE),
       );
     }
 
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
@@ -123,6 +123,7 @@ public function __isset($name) {
    */
   public function __unset($name) {
     $this->set($name, NULL);
+    unset($this->values[$name]);
   }
 
   /**