Wraps the current_index to the other side of the menu.

def __wrap_index(self):
        """Wraps the current_index to the other side of the menu."""
        if self.current_index < 0:
            self.current_index = len(self.gui_buttons) - 1
        elif self.current_index >= len(self.gui_buttons):
            self.current_index = 0