fix burned by burning/drowned in a drowning

fix burned by burning/drowned in a drowning

     From a bug report:  you could end up with
gravestone/logfile result of "burned by burning" or "drowned in a drowning".
If you get life-saved when drowning in water or burning in lava, the game
tries to teleport you to safety.  If the teleport fails for some reason--
such as lack of unoccupied non-water or non-lava locations--you drown or
burn again.  But life-saving was resetting the killer reason and the repeat
drowning/burning wasn't setting it up again, so the default got used and
produced a silly result.