Avoid override new_value info with None from old_value

[titaiwangms]

Users could have a well-defined new_value and use it to replace an old value which has less information.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.92%. Comparing base (c7b8908) to head (5c6bee7).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #227      +/-   ##
==========================================
- Coverage   76.94%   76.92%   -0.03%     
==========================================
  Files          40       40              
  Lines        4992     4992              
  Branches      996      996              
==========================================
- Hits         3841     3840       -1     
  Misses        864      864              
- Partials      287      288       +1     

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