commit 752fd38d1070e4d31ab226e8f4758658b9efe0c6
Author: Joel Pittet <joel@pittet.ca>
Date:   Sun Mar 9 15:16:30 2014 -0700

    remove output

diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index 045f184..0eec317 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -662,7 +662,6 @@ function template_preprocess_username(&$variables) {
     $link_options = isset($variables['link_options']) ? $variables['link_options'] : array();
     $variables['attributes']['href'] = url($variables['link_path'], $link_options);
   }
-  return $output;
 }
 
 /**