activescaffold belongs_to relationship giving routing error

I am using the following: Rails 3.0.3 Vhochstein's Fork for Activescaffold rake 0.9.0 ruby 1.9.2

I have a model called component which has a belongs_to relationship with category. This was modelled using activescaffold and was working quite well. I took a break for a couple of months and now that I got back to it activescafold gives a "ActionController::RoutingError (undefined method `class_name' for nil:NilClass):" error whenever I try to access the component model. I figured this is due to the relationship (belongs_to). If i remove the开发者_如何学Python relationship from the model, it works. If I add it back it fails!

Any Ideas?

Here is the Code:

Routes

  namespace :admin do 
resources :users,:roles,:vendors,:shipping_modes,:order_types,:sizes,
          :suppliers,:categories,:sub_categories, :material_types,:colours,
          :materials,:styles,:surcharges, :budget_templates, :budget_components do
  as_routes      
end 

end

Controller

class Admin::BudgetComponentsController < ApplicationController
layout 'site_admin'

active_scaffold :budget_component do |config|
  config.actions.exclude :delete,:update
  config.columns[:category].form_ui = :select 
  config.create.columns = [:name,:category]
  config.list.columns = [:name,:category]
  config.show.columns = [:name,:category]
  config.show.columns.add_subgroup "Time Details" do |name_group|
    name_group.add :created_at,:updated_at
  end

  config.list.sorting = {:name => 'ASC'}    
end
end

Model

class BudgetComponent < ActiveRecord::Base
  belongs_to :category

  validates_presence_of :name, :category_id
  validates_uniqueness_of :name
end

I had a similar problem. The solution is to add your nil:NilClass again, then it will work.