Fix deleting worn object

When going down stairs while punished, if you had quivered a mirror
and the mirror was dropped because you fell down the stairs, it would
not have been unequiped.

src/ball.c

@@ -976,6 +976,7 @@ litter(void)
                 You("drop %s and %s %s down the stairs with you.",
                     yname(otmp), (otmp->quan == 1L) ? "it" : "they",
                     otense(otmp, "fall"));
+                setnotworn(otmp);
                 freeinv(otmp);
                 hitfloor(otmp, FALSE);
             }