diff -u b/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
--- b/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -568,14 +568,15 @@
 function template_preprocess_rdf_metadata(&$variables) {
   foreach ($variables['metadata'] as $key => $attributes) {
-    // In some cases $attributes is not set. In those cases make it an array
-    // for when we construct the Attribute object below.
-    if (!isset($attributes)) {
-      $attributes = array();
-    }
     // The XHTML+RDFa doctype allows either <span></span> or <span /> syntax to
     // be used, but for maximum browser compatibility, W3C recommends the
     // former when serving pages using the text/html media type, see
     // http://www.w3.org/TR/xhtml1/#C_3.
-    $variables['metadata'][$key] = new Attribute($attributes);
+
+    if (!is_null($attributes)) {
+      $variables['metadata'][$key] = new Attribute($attributes);
+    }
+    else {
+      $variables['metadata'][$key] = new Attribute();
+    }
   }
 }