Dont initialize the association proxy for nil records

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1165 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/associations.rb

@@ -557,6 +557,7 @@ module ActiveRecord
           end
 
           define_method("set_#{association_name}_target") do |target|
+            return if target.nil?
             association = association_proxy_class.new(self,
               association_name, association_class_name,
               association_class_primary_key_name, options)

activerecord/test/associations_go_eager_test.rb

@@ -29,6 +29,10 @@ class EagerAssociationTest < Test::Unit::TestCase
     assert_equal 2, posts.first.comments.size
   end
 
+  def test_loading_with_no_associations
+    assert_nil Post.find(@authorless.id, :include => :author).author
+  end
+
   def test_eager_association_loading_with_belongs_to
     comments = Comment.find(:all, :include => :post)
     assert_equal @welcome.title, comments.first.post.title

activerecord/test/fixtures/posts.yml

@@ -11,3 +11,10 @@ thinking:
   title: So I was thinking
   body: Like I hopefully always am
   type: SpecialPost
+
+authorless:
+  id: 3
+  author_id: ""
+  title: I don't have any comments
+  body: I just don't want to
+  type: Post