Index: wp-includes/general-template.php
===================================================================
--- wp-includes/general-template.php	(revision 23183)
+++ wp-includes/general-template.php	(working copy)
@@ -1648,13 +1648,17 @@
 	} elseif ( is_category() ) {
 		$term = get_queried_object();
 
-		$title = sprintf( $args['cattitle'], get_bloginfo('name'), $args['separator'], $term->name );
-		$href = get_category_feed_link( $term->term_id );
+		if ( $term ) {
+			$title = sprintf( $args['cattitle'], get_bloginfo('name'), $args['separator'], $term->name );
+			$href = get_category_feed_link( $term->term_id );
+		}
 	} elseif ( is_tag() ) {
 		$term = get_queried_object();
 
-		$title = sprintf( $args['tagtitle'], get_bloginfo('name'), $args['separator'], $term->name );
-		$href = get_tag_feed_link( $term->term_id );
+		if ( $term ) {
+			$title = sprintf( $args['tagtitle'], get_bloginfo('name'), $args['separator'], $term->name );
+			$href = get_tag_feed_link( $term->term_id );
+		}
 	} elseif ( is_author() ) {
 		$author_id = intval( get_query_var('author') );