Bug reports belong in the Ubercart issue queue at http://drupal.org/project/issues/ubercart Please use the issue queue for things like this rather than post on ubercart.org.

PHP Notices are turned on by default in Drupal 7 (they were off by default in Drupal 6), which is why you see this notice in D7 and not D6. I've committed a change to check the existence of the 'settings' key before using it, which should eliminate the notice. The notice doesn't affect the operation of the code.