Through-association owner's primary key wasn't quoted. Generates inva…

…lid SQL (id = ) if the record wasn't saved yet (i.e. the primary key's value is nil).

activerecord/lib/active_record/associations/through_association_scope.rb

@@ -30,7 +30,7 @@ def construct_conditions
       # Associate attributes pointing to owner, quoted.
       def construct_quoted_owner_attributes(reflection)
         if as = reflection.options[:as]
-          { "#{as}_id"   => @owner[reflection.active_record_primary_key],
+          { "#{as}_id"   => @owner.class.quote_value(@owner[reflection.active_record_primary_key]),
             "#{as}_type" => reflection.klass.quote_value(
               @owner.class.base_class.name.to_s,
               reflection.klass.columns_hash["#{as}_type"]) }