Fix error validing account details on second try. Bug 775511
Fix error validing account details on second try. Bug 775511

* src/client/accounts/add-edit-page.vala
  (AddEditPage::get_account_information): Handle when the id is not null,
  but the account has not yet been added to the engine, as is the case
  when a new account has vailed validation and hence is an orphan.

tshikaboom/geary,tshikaboom/geary,tshikaboom/geary