commit 6b681cd5e1986e4bb1e0ee68d616a74d8c176bd0
Author: fago <nuppla@zites.net>
Date:   Thu Mar 21 13:35:59 2013 +0100

    Fixed isEmpty().

diff --git a/core/lib/Drupal/Core/TypedData/Type/Map.php b/core/lib/Drupal/Core/TypedData/Type/Map.php
index 1948278..338ff8e 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Map.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Map.php
@@ -197,9 +197,11 @@ public function isEmpty() {
         return FALSE;
       }
     }
-    foreach ($this->values as $name => $value) {
-      if (isset($value) && !isset($this->properties[$name])) {
-        return FALSE;
+    if (isset($this->values)) {
+      foreach ($this->values as $name => $value) {
+        if (isset($value) && !isset($this->properties[$name])) {
+          return FALSE;
+        }
       }
     }
     return TRUE;