-$last_menu_key = array_pop( array_keys( $menu ) );
-if ( 'wp-menu-separator' == $menu[ $last_menu_key ][ 4 ] )
+$last_menu_key = array_keys( $menu );
+$last_menu_key = array_pop( $last_menu_key );
+if ( !empty( $menu ) && 'wp-menu-separator' == $menu[ $last_menu_key ][ 4 ] )