Fix bug in dynamic BCE. With regression test.

Rationale:
We implicitly assumed anything on a fixed offset to a suitable
candidate could be picked for codegen. Although this is usually
true, the scanner found an exception (on types). So, it is best
to make the test explicit. Note: some type implications are TBD.

Bug:32193474

Test: test-art-host and offending APKs
Change-Id: I664a2caa97a7f231509f8832b940dd72da11a372