fix U1079 - loss of water walking over lava

fix U1079 - loss of water walking over lava

     Fix the reported problem of being able to safely stand on lava after
taking off fireproofed water walking boots.  The situation was more wide-
spread than that; the same thing happened when non-fireproofed boots were
burned off while walking over the lava in the first place.  Now you'll
fall in and end up getting stuck (you have to have fire resistance for any
of this to happen and that resistance makes falling in be survivable).