detecting attempts to address an invalid object.

Beyond Zork release 60 contains a bug wherein the dictionary entry for
the circlet is incorrectly treated as an object when blown.  This turned
out to be object number 41460 (or similar).  Its entry in the object
table would reside far outside the expanse of memory the Z-machine can
access.  Infocom's interpreter simply returns zero when the zcode
checked what turns out to be an invalid object and the game continues
running as if nothing was wrong.  Back when Zip was current, this bug
was worked around by checking if the game is Beyond Zork and the object
number was over an arbitrarily large number (2000) and if so just return
zero.  I rewrote this code to check ALL accesses to the object table,
throw a fatal error if the access is invalid, and return zero if the
game happens to be Beyond Zork.

See these resources for more information:
https://ifarchive.org/if-archive/infocom/interpreters/zip/zip_bugs.txt
https://intfiction.org/t/beyond-zork-passing-invalid-values-to-get-prop-addr/48347
https://intfiction.org/t/z-machine-undefined-behavior/44990
https://intfiction.org/t/z-machine-standard-unclear-aspects-ambiguities/64128