Don't try to translate tags in WP_Theme::translate_header() if we are not in the admin and get_theme_feature_list() isn't defined. see #20103.

git-svn-id: http://svn.automattic.com/wordpress/trunk@20668 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-theme.php

@@ -690,7 +690,7 @@ final class WP_Theme implements ArrayAccess {
 				$this->name_translated = translate( $value, $this->get('TextDomain' ) );
 				return $this->name_translated;
 			case 'Tags' :
-				if ( empty( $value ) )
+				if ( empty( $value ) || ! function_exists( 'get_theme_feature_list' ) )
 					return $value;
 
 				static $tags_list;