fix: Crash in Tracer for idle timeout

[philipphofmann]

📜 Description

dispatch_block_create can return NULL. If it does, we finish the transaction and don't schedule the timeout.

💡 Motivation and Context

Fixes GH-2832, GH-2769

💚 How did you test it?

Unit tests, and on an iPhone to validate UI event transactions are still working properly.

📝 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	6250.58 ms	6269.63 ms	19.05 ms
Size	20.76 KiB	426.11 KiB	405.34 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
49819af	1263.92 ms	1275.66 ms	11.74 ms
8f397a7	1230.10 ms	1253.88 ms	23.77 ms
fdfe96b	1227.90 ms	1242.56 ms	14.66 ms
d40512b	1231.12 ms	1244.54 ms	13.42 ms
c9724f9	1199.38 ms	1229.54 ms	30.16 ms
28333b6	1247.29 ms	1262.51 ms	15.22 ms
f576153	1210.02 ms	1228.94 ms	18.92 ms
0dedab7	1221.26 ms	1235.34 ms	14.08 ms
bd2afa6	1241.37 ms	1246.20 ms	4.83 ms
10ee2ce	1250.90 ms	1258.57 ms	7.67 ms

App size

Revision	Plain	With Sentry	Diff
49819af	20.76 KiB	427.31 KiB	406.55 KiB
8f397a7	20.76 KiB	420.55 KiB	399.79 KiB
fdfe96b	20.76 KiB	419.70 KiB	398.95 KiB
d40512b	20.76 KiB	427.77 KiB	407.00 KiB
c9724f9	20.76 KiB	427.66 KiB	406.90 KiB
28333b6	20.76 KiB	424.69 KiB	403.93 KiB
f576153	20.76 KiB	425.77 KiB	405.01 KiB
0dedab7	20.76 KiB	420.00 KiB	399.24 KiB
bd2afa6	20.76 KiB	420.55 KiB	399.79 KiB
10ee2ce	20.76 KiB	427.77 KiB	407.00 KiB

Previous results on branch: fix/crash-in-tracer-idle-timeout

Startup times

Revision	Plain	With Sentry	Diff
ff0832c	1233.57 ms	1256.45 ms	22.88 ms

App size

Revision	Plain	With Sentry	Diff
ff0832c	20.76 KiB	426.14 KiB	405.38 KiB

[brustolin]

Looks good.

Just one suggestion.

[brustolin]

m: I would just add a comment here that the transaction will not be send because it does not have any child.

[philipphofmann]

Better now?

[codecov]

Codecov Report

Merging #2834 (b5bafcd) into main (fb53d97) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2834      +/-   ##
==========================================
- Coverage   81.33%   81.33%   -0.01%     
==========================================
  Files         258      258              
  Lines       24131    24142      +11     
  Branches    10708    10712       +4     
==========================================
+ Hits        19628    19636       +8     
- Misses       4005     4007       +2     
- Partials      498      499       +1     

Impacted Files	Coverage Δ
Sources/Sentry/SentryDispatchQueueWrapper.m	100.00% <100.00%> (ø)
Sources/Sentry/SentryTracer.m	96.28% <100.00%> (-0.34%)	⬇️

... and 7 files with indirect coverage changes

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