show proper error when all articles are deselected in order edit

app/controllers/orders_controller.rb

@@ -5,6 +5,7 @@
 class OrdersController < ApplicationController
   
   before_filter :authenticate_orders
+  before_filter :remove_empty_article, only: [:create, :update]
   
   # List orders
   def index
@@ -174,4 +175,8 @@ class OrdersController < ApplicationController
     notice.join(', ')
   end
 
+  def remove_empty_article
+    params[:order][:article_ids].reject!(&:blank?) if params[:order] and params[:order][:article_ids]
+  end
+
 end

app/views/orders/_form.html.haml

@@ -48,6 +48,8 @@
     %tr
       %td
         = check_box_tag 'checkall', "1", false, { 'data-check-all' => '#articleList' }
+        -# also when all are deselected, make sure this parameter is sent (controller removes empty values again)
+        = hidden_field_tag "order[article_ids][]", nil
       %td{:colspan => "6"}= t '.select_all'
 
   - if (@template_orders && !@template_orders.empty?)