andthen returns Empty on failure

S03-operators/andthen.t

@@ -6,7 +6,7 @@ is (1 andthen 2), 2, 'andthen basics';
 is (1 andthen 2 andthen 3), 3, 'andthen chained';
 is (0 andthen 1), 1, 'definedness, not truthness';
 ok Any === (1 andthen Any), 'first undefined value (1)';
-ok Any === (Any andthen 2), 'first undefined value (2)';
+ok Empty === (Any andthen 2), 'first undefined value (2)';
 my $tracker = 0;
 nok (Int andthen ($tracker = 1)), 'sanity';
 nok $tracker, 'andthen thunks';