Olga draws a check payable to Sven. Sven indorses the back of the check "without recourse" and negotiates the check to Hansel who in turn negotiates the check by a blank indorsement and delivers the check to Gretta. Gretta deposits the check in her checking account. If the bank dishonors the check because Olga has filed for bankruptcy and returns the check to Gretta, who has liability on the check?