I agree 破蛹成蝶.
The reason is that, if you couldn't afford a boundle X, but now you can,
it implies nothing! WARP remains valid.
WARP only says onething: If in period b, you can afford B and T, but you choose b,
it must be because T is inferior. Thus, once you were observed choosing T
(,say, in period t,) we can infer that B is not affordable.
But, if B is chosen while T is not affordable, then once T being chosen
doesn't mean increase in welfare.
Draw a graph and things will become clear.