refs https://github.com/TryGhost/Ghost/pull/13091
- When the job is run under Node v14 with SQLite DB the parentPort is `null` in some of the environments. The guarding code protects from the job crashing in such situation.
- The most probable cause is running btrheds with `BTHREADS_BACKEND = 'child_process';` configuration for SQLite. Should be fixed once https://github.com/mapbox/node-sqlite3/issues/1386 is properly resolved
