Fix crash in MulticastDelegate caused by concurrent accesses

[laevandus]

🔗 Issue Links

Resolves PBE-5434

🎯 Goal

Make MulticastDelegate thread-safe

🛠 Implementation

We got a report of crashes in the MulticastDelegate what point at multi-threading issues..

Fatal Exception: NSGenericException
0  CoreFoundation                 0x83f20 __exceptionPreprocess
1  libobjc.A.dylib                0x16018 objc_exception_throw
2  CoreFoundation                 0x18220c -[__NSSingleObjectEnumerator init]
3  Foundation                     0x29284 -[NSConcreteHashTable countByEnumeratingWithState:objects:count:]
4  Foundation                     0x291f8 -[NSConcreteHashTable allObjects]
5  <Redacted>                      0x87dd44 specialized MulticastDelegate.mainDelegate.getter
6  <Redacted>                       0x87f570 specialized MulticastDelegate.invoke(_:)
7  <Redacted>                       0x914c60 specialized DelegateCallable.delegateCallback(_:) + 95 (DataController.swift:95)

🧪 Manual Testing Notes

Explain how this change can be tested manually, if applicable.

☑️ Contributor Checklist

• I have signed the Stream CLA (required)
• This change should be manually QAed
• Changelog is updated with client-facing changes
• Changelog is updated with new localization keys
• New code is covered by unit tests
• Comparison screenshots added for visual changes
• Affected documentation updated (docusaurus, tutorial, CMS)

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	6.76MB	6.82MB	0.06MB	🟢
StreamChatUI	4.41MB	4.41MB	0.0MB	🟢

[Stream-SDK-Bot]

SDK Performance

target	metric	benchmark	branch	performance	status
MessageList	Hitches total duration	10 ms	5.01 ms	49.9% 🔼	🟢
	Duration	2.6 s	2.56 s	1.54% 🔼	🟢
	Hitch time ratio	4 ms per s	1.96 ms per s	51.0% 🔼	🟢
	Frame rate	75 fps	78.27 fps	4.36% 🔼	🟢
	Number of hitches	1	0.4	60.0% 🔼	🟢
ChannelList	Hitches total duration	12.5 ms	11.68 ms	6.56% 🔼	🟢
	Duration	2.6 s	2.55 s	1.92% 🔼	🟢
	Hitch time ratio	5 ms per s	4.59 ms per s	8.2% 🔼	🟢
	Frame rate	72 fps	74.3 fps	3.19% 🔼	🟢
	Number of hitches	1.2	1.0	16.67% 🔼	🟢

[nuno-vieira]

Looks good, just added a question 👍

[nuno-vieira]

LGTM! ✅

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	6.76MB	6.79MB	0.03MB	🟢
StreamChatUI	4.41MB	4.41MB	0.0MB	🟢

[sonarqubecloud]

Quality Gate passed

Issues
153 New issues
0 Accepted issues

Measures
0 Security Hotspots
84.6% Coverage on New Code
0.1% Duplication on New Code

See analysis details on SonarCloud