set default category_id instead of the object (#11665)

Rails 2.3 still has issues with synchronizing the association_id
and association attributes of an object. That means, if you set the
association with an object first and then just set the id afterwards,
the object wins and the setting of the id gets lost.

This is not an issue in Rails >= 3.1 anymore.

Contributed by Holger Just.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/1.4-stable@10226 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/document.rb

@@ -42,7 +42,9 @@ class Document < ActiveRecord::Base
   def initialize(attributes=nil, *args)
     super
     if new_record?
-      self.category ||= DocumentCategory.default
+      # Rails3 use this instead
+      # self.category ||= DocumentCategory.default
+      self.category_id = DocumentCategory.default.id if self.category_id == 0
     end
   end