You can glue splits and/or fill them but at the end of the day, it will still look like a bowl with a split in it, which if you are trying to sell it, might put off some customers.
Duncan is on the right track - if it's safe to put on the lathe, turn the crack away or if not, cut a section off. Sometimes I would cut a blank through the crack and make a smaller blank without a crack but it depends on the blank and what could be salvaged.
Another way out would be to just cut a slice of the side of the blank to remove the crack and re-cut to a slightly smaller circle. Occasionally with blanks like that I just move the centre at the beginning so the crack gets turned away but turning a blank off centre induces some vibration so it would depend on the size of the blank and the amount of offset needed.