several isssues with registration process

Test on ez4.1 (should be the same another version)
Try to register a new user. Click several time on the button create account
-> A nice ezpublish fatal error will be display:

1 Valide account will be create
1 wrong account will be create (empty object)
The empty account is a draft (it can be remove by a script ) but why the system don't rollback the transaction?