ive had this happen to hickory while trying to heat treat the belly. i keep my eyes open for it now, with a bottle of superglue right handy. as soon as i find a crack developing, i run a bead of the superglue down the crack, and spread it in with my finger. the wood is still VERY hot so the glue soaks right in. ive never had any problems with these cracks. but like they said, you might if they run off the edge.
Phil