Work around a strange piece of Syck behaviour where it checks...

Work around a strange piece of Syck behaviour where it checks Model#respond_to? before initializing the object.

Things like YAML.load(YAML.dump(@post)) won't work without this.

activerecord/lib/active_record/attribute_methods.rb

@@ -54,7 +54,7 @@ def respond_to?(*args)
 
     protected
       def attribute_method?(attr_name)
-        attr_name == 'id' || @attributes.include?(attr_name)
+        attr_name == 'id' || (defined?(@attributes) && @attributes.include?(attr_name))
       end
   end
 end

activerecord/test/cases/attribute_methods_test.rb

@@ -85,6 +85,17 @@ def test_respond_to?
     assert !topic.respond_to?("nothingness")
     assert !topic.respond_to?(:nothingness)
   end
+  
+  
+  # Syck calls respond_to? before actually calling initialize
+  def test_respond_to_with_allocated_object
+    topic = Topic.allocate
+    assert !topic.respond_to?("nothingness")
+    assert !topic.respond_to?(:nothingness)
+    assert_respond_to topic, "title"
+    assert_respond_to topic, :title
+  end
+  
 
   def test_array_content
     topic = Topic.new