If Sound the Call resolves while all graveyards are empty, first a 1/1 token is created, then the Sound the Call card is put into your graveyard, which makes the token 2/2. Although the token is momentarily 1/1, state-based actions aren't checked until after the Sound the Call card used to create the token is in a graveyard. For example, if Night of Souls' Betrayal is on the battlefield, the Wolf will momentarily be 0/0. By the time state-based actions are checked, it will be 1/1, so it will remain on the battlefield.