Use a monkey patch instead of hacking code

Refs johnny/jquery-sortable#122

Author: daftspunk

modules/system/assets/ui/js/drag.sort.js

@@ -144,6 +144,15 @@
         this.dispose()
     }
 
+    // External solution for group persistence
+    // See https://github.com/johnny/jquery-sortable/pull/122
+    Sortable.prototype.destroyGroup = function() {
+        var jqSortable = this.$el.data('jqSortable')
+        if (jqSortable.group) {
+            jqSortable.group._destroy()
+        }
+    }
+
     Sortable.DEFAULTS = {
         useAnimation: false,
         usePlaceholderClone: false,

modules/system/assets/ui/vendor/sortable/jquery-sortable.js

@@ -631,10 +631,6 @@
           return val != that
         })
 
-      // See https://github.com/johnny/jquery-sortable/pull/122
-      if(this.group)
-        this.group._destroy()
-
       $.each(this.items || [], function(){
         $.removeData(this, subContainerKey)
       })