a woman dressed indecently with attract more attention than one wearing hijab, therefore the former is more prone to assault. the sin of rape is on the rapist, but i think the victim if she was dressed indecently was not taking precautions to prevent the crime. its like locking your front door to keep away burglars, you can leave your home wide open and it could get robbed. the sin of robbery is not yours, but you could have done something to prevent it.