Issue #2218849 by hellboy2k8: Remove unused line from twig_render_template().

core/themes/engines/twig/twig.engine

@@ -47,7 +47,6 @@ function twig_init(Extension $theme) {
  *   The output generated by the template, plus any debug information.
  */
 function twig_render_template($template_file, $variables) {
-  $variables['_references'] = array();
   $output = array(
     'debug_prefix'    => '',
     'debug_info'      => '',