Missing index check on desc_table array access in runtime deserialization pony_deserialise_offset about ponyc HOT 3 OPEN

Additional context: https://ponylang.zulipchat.com/#narrow/stream/190365-runtime/topic/Unsafe.20deserialise.20exploitation

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We don't have any good way to deal with errors of this sort in the serialization of this sort. Some investigation of what we should do when we get unexpected values. Serialization was written for "totally trusted/may segfault". We probably want to throw an error but we need to verify that we are always good for doing it.

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What probably needs to happen for the error case is to call the "throw fn" passed to pony_deserialise with some code like this:

      serialise_cleanup(ctx);
      ctx->serialise_throw();
      abort();

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