Update some of the unit tests for the standard `arg/3` predicate to try to delay the expected error to runtime
Update some of the unit tests for the standard `arg/3` predicate to try to delay the expected error to runtime

LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3