buried punishment ball

Prevent burying a ball from ending your punishment.

When you bury the ball, internally NetHack Punishment
ceases, but a new trap type of TT_BURIEDBALL  immediately
kicks in (acting similar to TT_INFLOOR in some ways).
You can eventually work the ball free (or teleport, etc.),
but that will just return you back to normal Punishment.

src/sit.c

@@ -91,7 +91,7 @@ dosit()
 		    You("sit in the lava!");
 		    u.utrap += rnd(4);
 		    losehp(d(2,10), "sitting in lava", KILLED_BY);
-		} else if(u.utraptype == TT_INFLOOR) {
+		} else if(u.utraptype == TT_INFLOOR || u.utraptype == TT_BURIEDBALL) {
 		    You_cant("maneuver to sit!");
 		    u.utrap++;
 		}