extraneous "break" in node_type_form_validate causes fatal error

This is a sub-part of the larger patch proposed and already reviewed here: http://drupal.org/node/88633

If you submit a new node type with the same name as an existing type you get this very unfortunate error:

Fatal error: Cannot break/continue 1 level in /Users/Shared/www/drupal/modules/node/content_types.inc on line 246

attached patch removes the offending "break" command.