Remove uneeded local var definition.

activerecord/lib/active_record/nested_attributes.rb

@@ -322,9 +322,8 @@ def _destroy
     def assign_nested_attributes_for_one_to_one_association(association_name, attributes)
       options = self.nested_attributes_options[association_name]
       attributes = attributes.with_indifferent_access
-      check_existing_record = (options[:update_only] || !attributes['id'].blank?)
 
-      if check_existing_record && (record = send(association_name)) &&
+      if (options[:update_only] || !attributes['id'].blank?) && (record = send(association_name)) &&
           (options[:update_only] || record.id.to_s == attributes['id'].to_s)
         assign_to_or_mark_for_destruction(record, attributes, options[:allow_destroy]) unless call_reject_if(association_name, attributes)