Fix structure title (page slide)

app/assets/javascripts/lib/jquery.mjs.nestedSortable.js

@@ -240,7 +240,7 @@
 
 
 			// for Orbit ----> Check the number of pages in each page
-				if($('#items').length) {
+				if($('.item-groups').length) {
 					var $sortable = $('.sortable'),
 						$host = $sortable.children('.navbar').eq(0),
 						$navbar = $('.sortable li').children('.navbar'),