Avoid crashing in SentryCoreDataTracker

[bjhomer]

📜 Description

Users can pass in a nil error parameter when calling Core Data methods like save: and executeFetchRequest:. We were incorrectly handling that nil error parameter and trying to dereference it inside SENTRY_LOG_DEBUG calls. This commit fixes that by instead checking the result of the call, as recommended by the Cocoa Error Handling Guide.

💡 Motivation and Context

This fixes #3151.

💚 How did you test it?

Honestly, I didn't. But I'm making the logging logic match the same logic used in [fetchSpan finishWithStatus:]

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[bjhomer]

I swapped the order of the parameters here to make the logic in the logging mirror the logic in the [span finishWithStatus:] call above.

Previously, this logging was almost always incorrect; it was just checking whether the user had passed in an error pointer. If so, it logged "error".

[bjhomer]

If result is true, then the call succeeded, and we should log ok. We have no guarantee about the state of error in this case.

If result is false, then there was an error. If the user passed in an error pointer, it will now point to the error. But if the user passed in nil, then error will still be nil, and dereferencing it would cause a crash. In either case, we don't need the actual details of the error here at all; we only need to know whether an error happened, and that can be determined entirely by looking at the result.

[bjhomer]

This was partially fixed in https://github.com/getsentry/sentry-cocoa/issues/2433, but the logging still retained the old logic, so the crash remained. This PR fixes the logging logic.

[codecov]

Codecov Report

Merging #3152 (59161ef) into main (d760c3f) will decrease coverage by 0.008%.
The diff coverage is 100.000%.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3152       +/-   ##
=============================================
- Coverage   89.133%   89.126%   -0.008%     
=============================================
  Files          502       502               
  Lines        53965     53957        -8     
  Branches     19329     19321        -8     
=============================================
- Hits         48101     48090       -11     
+ Misses        5008      4898      -110     
- Partials       856       969      +113     

Impacted Files	Coverage Δ
Sources/Sentry/SentryCoreDataTracker.m	95.683% <100.000%> (ø)

... and 30 files with indirect coverage changes

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[philipphofmann]

Thanks, @bjhomer, for the fix. I will fix the Changelog and add some tests in a subsequent PR, as I want to get a hotfix out quickly.