sqlops: safety check for result row field

- it might not be set in case of a failure in the middle of result
  conversion from db to internal memory
- freeing the partial result could result in a crash
- reported by Juha Heinanen

(cherry picked from commit f27df26ca01394250cbe12c5ccf694c6afd3707f)
(cherry picked from commit 20276e667631ec281851c2ef58d71863ae2318c4)