Do not include null on serialized model

[jonesbusy]

Description

Do not include null on serilized model

Testing done

None. CI

Submitter checklist

• I have read and understood the CONTRIBUTING guide
• I have run mvn license:update-file-header, mvn spotless:apply, pre-commit run -a, mvn clean install before opening the PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.52%. Comparing base (954431f) to head (347853c).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #705      +/-   ##
============================================
+ Coverage     86.96%   87.52%   +0.56%     
  Complexity      968      968              
============================================
  Files            44       44              
  Lines          3015     3015              
  Branches        379      379              
============================================
+ Hits           2622     2639      +17     
+ Misses          232      215      -17     
  Partials        161      161              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.