fix: Crash when adding a crumb for a timezone change

[philipphofmann]

📜 Description

Fix a crash when adding a time crumb for a timezone change and the previously stored timezone offset is nil.

💡 Motivation and Context

Fixes #3513.

💚 How did you test it?

Unit tests.

📝 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

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1195.67 ms	1206.02 ms	10.35 ms
Size	21.58 KiB	418.53 KiB	396.95 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
51307b7	1232.22 ms	1235.60 ms	3.38 ms
3437454	1235.54 ms	1244.82 ms	9.28 ms
7bb0873	1193.70 ms	1222.74 ms	29.04 ms
dd0557f	1242.04 ms	1250.86 ms	8.82 ms
7bc3c0d	1261.16 ms	1278.38 ms	17.22 ms
9d56232	1192.09 ms	1228.86 ms	36.77 ms
5f8ee7a	1249.48 ms	1252.20 ms	2.72 ms
326b7eb	1231.06 ms	1243.56 ms	12.50 ms
25a5e8b	1249.18 ms	1268.42 ms	19.24 ms
216bdf9	1196.29 ms	1209.80 ms	13.51 ms

App size

Revision	Plain	With Sentry	Diff
51307b7	22.85 KiB	407.63 KiB	384.78 KiB
3437454	22.85 KiB	408.88 KiB	386.03 KiB
7bb0873	22.85 KiB	407.09 KiB	384.24 KiB
dd0557f	22.85 KiB	411.75 KiB	388.90 KiB
7bc3c0d	20.76 KiB	427.36 KiB	406.59 KiB
9d56232	20.76 KiB	425.80 KiB	405.04 KiB
5f8ee7a	22.85 KiB	411.93 KiB	389.08 KiB
326b7eb	20.76 KiB	432.31 KiB	411.55 KiB
25a5e8b	20.76 KiB	436.33 KiB	415.57 KiB
216bdf9	21.58 KiB	418.13 KiB	396.54 KiB

Previous results on branch: fix/crash-in-timezoneEventTriggered

Startup times

Revision	Plain	With Sentry	Diff
122ae54	1225.45 ms	1246.65 ms	21.20 ms
38d50a0	1223.11 ms	1238.91 ms	15.81 ms

App size

Revision	Plain	With Sentry	Diff
122ae54	21.58 KiB	418.57 KiB	396.98 KiB
38d50a0	21.58 KiB	418.44 KiB	396.86 KiB

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b9a9ffd) 89.183% compared to head (182f5aa) 89.222%.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3524       +/-   ##
=============================================
+ Coverage   89.183%   89.222%   +0.038%     
=============================================
  Files          528       528               
  Lines        57534     57581       +47     
  Branches     20611     20633       +22     
=============================================
+ Hits         51311     51375       +64     
+ Misses        5310      5292       -18     
- Partials       913       914        +1     

Files	Coverage Δ
Sources/Sentry/SentrySystemEventBreadcrumbs.m	100.000% <100.000%> (ø)
...Breadcrumbs/SentrySystemEventBreadcrumbsTest.swift	97.991% <100.000%> (+0.110%)	⬆️

... and 21 files with indirect coverage changes

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