There is no -0n, and we'd therefore never serialize such a BigInt.
But we can't trust serialized data to not have gotten corrupted
(or be fuzzer-generated), so guard against this case when
deserializing.

Fixed: chromium:1359937
Change-Id: If11d9a364480bae51911cc4a0ce8a719853139fe
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3904414Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83362}