Yes, I agree. That should not have been left out. Add these two lines after the last one (religion) in the array of fields in the same file you edited earlier
new WT_Census_CensusColumnOccupation($this, 'Occupation', 'Chief occupation, or trade'),
new WT_Census_CensusColumnNull($this, 'Employment', 'Employer, Worker, or Own Account'),
That adds column 18 and a single column to replace 19, 20, and 21. I’m assuming that col 18 “Employment other than at chief occupation or trade, if any” is not necessary.