Nav helper bug - home page always marked as current

- fixed a bug whereby once you visit the homepage the homepage menu item is always marked as the active page
- this was due to passing the config object being done by reference rather than by value, and therefore setting the selected item was persisted.

core/frontend/filters/index.js

@@ -6,8 +6,12 @@ coreFilters = function (ghost) {
     ghost.registerFilter('ghostNavItems', defaultCoreFilterPriority, function (args) {
         var selectedItem;
 
-        // Set the nav items based on the config
-        args.navItems = ghost.config().nav;
+        // we want to clone the config so the config remains unchanged
+        // we will need to make this recursive if we start supporting
+        // hierarchical menus
+        args.navItems = _.map(ghost.config().nav, function (value) {
+            return Object.create(value);
+        });
 
         // Mark the current selected Item
         selectedItem = _.find(args.navItems, function (item) {