HPCC-8924 Prevent simple recursive computerTypes causing stack faults

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4063 from ghalliday/issue8924

HPCC-8924 Prevent simple recursive computerTypes causing stack faults

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>