No reproduction scenario
You have only a stack trace, and can’t find a path of execution that reproduces erroneous data.
- Write a unit test that should crash.❌
- try to fix production code.
- Check that newly created test pass. ✅
Code is not testable ?
Refactor until code is turns testable 🤷♂️.
You can reproduce crash ?
Guess what ? exactly the same applies. Add a test to your test suite to check crash never comes back.