Fix issue216: take care of the case with job field with null value

[tom-tan]

This request is to fix #216.

It was introduced by #209 due to missing the case with job field with explicit null value.
This request fixes it by adding the case with job: null in addition to the case of missing job field.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.27%. Comparing base (12a0f7c) to head (1849dcb).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
+ Coverage   81.01%   81.27%   +0.25%     
==========================================
  Files           8        8              
  Lines         785      785              
  Branches      199      199              
==========================================
+ Hits          636      638       +2     
+ Misses        113      111       -2     
  Partials       36       36              

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[mr-c]

Thank you @tom-tan !