commit c8cedb309ac0930fd357c92d7a11ea55fb439244
Author: Joel Pittet <joel@pittet.ca>
Date:   Fri Jan 31 11:14:06 2014 -0800

    cleaner property union

diff --git a/core/includes/form.inc b/core/includes/form.inc
index daa17a6..034df83 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -2788,13 +2788,8 @@ function template_preprocess_form_element(&$variables) {
 
   // Add label_display and label variables to template.
   $variables['label_display'] = $element['#title_display'];
-  $variables['label'] = array(
-    '#theme' => 'form_element_label',
-    '#required' => isset($element['#required']) ? $element['#required'] : '',
-    '#title' => isset($element['#title']) ? $element['#title'] : '',
-    '#title_display' => isset($element['#title_display']) ? $element['#title_display'] : '',
-    '#id' => isset($element['#id']) ? $element['#id'] : '',
-  );
+  $variables['label'] = array('#theme' => 'form_element_label');
+  $variables['label'] += array_intersect_key($element, array_flip(array('#id', '#required', '#title', '#title_display')));
 
   $variables['children'] = $element['#children'];
 }