commit 65c0079a6789f218586e8ed8ba474012a27d3d51
Author: Klaus Purer <klaus.purer@gmail.com>
Date:   Sat Jul 13 13:45:39 2013 +0200

    Fixed isEmpty() method of email item class.

diff --git a/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
index 70f6b4c..599a3c3 100644
--- a/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
@@ -64,6 +64,7 @@ public function setValue($values, $notify = TRUE) {
         $value = $values[$name];
       }
       $property->setValue($value, FALSE);
+      unset($this->values[$name]);
     }
     // Notify the parent of any changes.
     if ($notify && isset($this->parent)) {
diff --git a/core/lib/Drupal/Core/Entity/Plugin/DataType/EmailItem.php b/core/lib/Drupal/Core/Entity/Plugin/DataType/EmailItem.php
index b147976..254505c 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/DataType/EmailItem.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/DataType/EmailItem.php
@@ -52,6 +52,7 @@ public function getPropertyDefinitions() {
    * {@inheritdoc}
    */
   public function isEmpty() {
-    return !isset($this->values['value']) || $this->values['value'] === '';
+    $value = isset($this->values['value']) ? $this->values['value'] : $this->get('value')->getValue();
+    return !isset($value) || $value === '';
   }
 }