Account Refunds and Transfers; you can Cancel "Override User credentials" and still continue

The "Override User credentials" in Account Refunds and Transfers can be cancelled and this incorrectly allows the wizard to continue.

To recreate:

1. Login with a User denied permission key "Account.Withdrawal.OverCreditLimit" - default is deny, so basically a user that isn't an Administrator.
2. Go to Transactions, Account Refund wizard.
3. Select an Account where the Credit Limit is exceeded and enter details.
4. Click Next.
5. Warns Credit Limit exceeded, click to override.
6. Override User Credentials dialog, click Cancel.

This allows wizard to continue. Note, the Business Layer allows this to proceed - this permission key is a User Interface only permission