Rescue condition for model nil

app/controllers/pages_controller.rb

@@ -188,11 +188,13 @@ class PagesController < ApplicationController
         @item = Item.where(:category => category_ids).first
       else
         if params[:action] && params[:action] == "show_from_link"
-            model = params[:app_action].classify.constantize
+            model = params[:app_action].classify.constantize rescue nil
+            if !model.nil?
               item = model.find(params[:id])
               @item = Item.where(:category => [item.category_id.to_s]).first
             end
         end
+      end
     
       @item = Item.root.children.where(:module_app_id => module_app.id).first unless @item
     end