? .patch
? uid_null.patch
Index: user.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/migrate/plugins/destinations/Attic/user.inc,v
retrieving revision 1.1.4.7
diff -u -F '^f' -p -r1.1.4.7 user.inc
--- user.inc	3 Jul 2010 17:07:04 -0000	1.1.4.7
+++ user.inc	14 Oct 2010 23:30:11 -0000
@@ -97,6 +97,12 @@ class MigrateDestinationUser extends Mig
     if (isset($row->migrate_map_destid1)) {
       $account->uid = $row->migrate_map_destid1;
     }
+    else {
+      // Prevents notice in user_save()
+      if (!isset($account->uid)) {
+        $account->uid = NULL;
+      }
+    }
 
     $this->prepare($migration, $account, $row);
     migrate_instrument_start('user_save');