Stop respond_to? from throwing when instances are created 'irregularly' i.e....

Stop respond_to? from throwing when instances are created 'irregularly' i.e. yaml loads.  [zenspider] Closes #4587


git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4172 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Allow AR::Base#respond_to? to behave when @attributes is nil [zenspider]
+
 * Support eager includes when going through a polymorphic has_many association. [Rick]
 
 * Added support for eagerly including polymorphic has_one associations. (closes #4525) [Rick]

activerecord/lib/active_record/base.rb

@@ -1587,7 +1587,9 @@ def hash
       # A Person object with a name attribute can ask person.respond_to?("name"), person.respond_to?("name="), and
       # person.respond_to?("name?") which will all return true.
       def respond_to?(method, include_priv = false)
-        if attr_name = self.class.column_methods_hash[method.to_sym]
+        if @attributes.nil?
+          return super 
+        elsif attr_name = self.class.column_methods_hash[method.to_sym]
           return true if @attributes.include?(attr_name) || attr_name == self.class.primary_key
           return false if self.class.read_methods.include?(attr_name)
         elsif @attributes.include?(method_name = method.to_s)