bank statement - default value for balance_start

In addons/account/account_bank_statement.py, class account.bank.statement, the default value for balance_start is calculated in the _default_balance_start method. However, in that method, the select is executed always against journal_id = 1. The default value for journal_id is calculated in the _default_journal_id method, where the journal selected is filtered by a domain clause based on the context. I think that the _default_balance_start method should also select the journal as the _default_journal_id method is done instead of using journal_id = 1.