[Wasm GC] Fix a trapsNeverHappen corner case with if/select of a trapping arm (#5681)

The logic says that if an if/select has an arm that returns a null type, and the if/select
goes into a cast, then we can ignore that arm in tnh mode (as it would trap, and we
are ignoring the possibility of a trap). But it is not enough to return a null type - the
null must actually flow out, rather than say a return be executed before.

One existing test needed adjustment, as it used calls for "thing with effects". But a
call can transfer control flow when EH is enabled, and this pass has -all. Rather
than mess with the features, I switched the effects to be locals.

0 files changed, 0 insertions, 0 deletions