fix: crash when call SentryUIApplication in background thread

[mlch911]

📜 Description

Fix crash when call SentryUIApplication in background thread. #3836

💡 Motivation and Context

💚 How did you test it?

📝 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

[brustolin]

Hello @mlch911, thanks for the help.
Since the problem occurs only during initialization, and, the responsibility to call every other SentryUIApplication function from the main thread lies with the caller, I believe we should only change the init function.

I need to check tho what is triggering the initialization. because just pushing it to a background thread may not be enough.

[mlch911]

Hello @mlch911, thanks for the help. Since the problem occurs only during initialization, and, the responsibility to call every other SentryUIApplication function from the main thread lies with the caller, I believe we should only change the init function.

I need to check tho what is triggering the initialization. because just pushing it to a background thread may not be enough.

This is not only occurs during initialization. Our app encounter this crash rarely when the network monitoring occurs at background thread just after we init sentry in main thread.

Here is the crash stack.

-[MaxWindow initWithFrame:] (MaxWindow.m:24)
-[AppDelegate window] (AppDelegate.m:184)
-[SentryUIApplication windows] (SentryUIApplication.m:84)
-[SentryCrashWrapper enrichScope:] (SentryCrashWrapper.m:187)
-[SentryHub initWithClient:andScope:] (SentryHub.m:80)
+[SentrySDK currentHub] (SentrySDK.m:76)
-[SentryRequestOperation initWithSession:request:completionHandler:]_block_invoke (SentryRequestOperation.m:37)

My code fixes crash in this case.

There may be other scenarios that can cause similar crashes. More sophisticated consideration may be needed.

[codecov]

Codecov Report

Attention: Patch coverage is 84.09091% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 90.608%. Comparing base (eb077dd) to head (8269d26).

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3855       +/-   ##
=============================================
- Coverage   90.672%   90.608%   -0.064%     
=============================================
  Files          579       579               
  Lines        45283     45295       +12     
  Branches     16121     16118        -3     
=============================================
- Hits         41059     41041       -18     
- Misses        4044      4184      +140     
+ Partials       180        70      -110     

Files	Coverage Δ
Sources/Sentry/SentryUIApplication.m	45.299% <100.000%> (+0.951%)	⬆️
Sources/Sentry/SentryDispatchQueueWrapper.m	86.274% <50.000%> (-13.726%)	⬇️

... and 32 files with indirect coverage changes

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