Use find instead of find_by_id

Better raise a 404 HTML NotFound exception than any other unexpected error.

app/controllers/admin/budget_groups_controller.rb

@@ -46,11 +46,11 @@ class Admin::BudgetGroupsController < Admin::BaseController
   private
 
     def load_budget
-      @budget = Budget.includes(:groups).find(params[:budget_id])
+      @budget = Budget.find_by_slug_or_id! params[:budget_id]
     end
 
     def load_group
-      @group = @budget.groups.find(params[:id])
+      @group = @budget.groups.find_by_slug_or_id! params[:id]
     end
 
     def groups_index