public Optional<Slot> getFirstEmptySlot() {
        int ret = this.inventory.firstEmpty();
        if (ret < 0) {
            return Optional.empty();
        }
        return Optional.of(getSlot(ret));
    }
Gets the initial title which was set when this GUI was made

@return the initial title used when this GUI was made
helper/src/main/java/me/lucko/helper/menu/Gui.java