Adding null course units information check

[DGoiana]

Closes #[issue number]
[Description of the changes proposed in the pull request. Include steps to replicate the behavior and screenshots if UI is updated]

Review checklist

• Terms and conditions reflect the current change
• Contains enough appropriate tests
• If aimed at production, writes a new summary in whatsnew/whatsnew-pt-PT
• Properly adds an entry in changelog.md with the change
• If PR includes UI updates/additions, its description has screenshots
• Behavior is as expected
• Clean, well-structured code

[codecov]

Codecov Report

Attention: Patch coverage is 12.50000% with 21 lines in your changes missing coverage. Please review.

Project coverage is 11%. Comparing base (fc9e349) to head (5bc73f9).
Report is 8 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #1332   +/-   ##
=======================================
+ Coverage       11%     11%   +1%     
=======================================
  Files          268     268           
  Lines         7310    7330   +20     
=======================================
+ Hits           799     802    +3     
- Misses        6511    6528   +17     

[limwa]

LGTM 🚀