NSInvalidArgumentException: attempt to insert nil object from objects[2]

[jpsim]

Describe the bug

We're seeing an increase in uncaught runtime exceptions coming from Foundation in our latest integration of the Bugsnag SDK on iOS.

NSInvalidArgumentException: *** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[2]

0  CoreFoundation          ___exceptionPreprocess
1  libobjc.A.dylib         _objc_exception_throw
2  CoreFoundation          __CFThrowFormattedException
3  CoreFoundation          -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]
4  CoreFoundation          +[NSDictionary dictionaryWithObjects:forKeys:count:]
5  [REDACTED]              __58-[BugsnagSessionTrackingApiClient deliverSessionsInStore:]_block_invoke ([REDACTED])
6  Foundation              ___NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__
7  Foundation              -[NSBlockOperation main]
8  Foundation              -[__NSOperationInternal _start:]
9  Foundation              ___NSOQSchedule_f
10 libdispatch.dylib       __dispatch_block_async_invoke2
11 libdispatch.dylib       __dispatch_client_callout
12 libdispatch.dylib       __dispatch_continuation_pop$VARIANT$mp
13 libdispatch.dylib       __dispatch_async_redirect_invoke
14 libdispatch.dylib       __dispatch_root_queue_drain
15 libdispatch.dylib       __dispatch_worker_thread2
16 libsystem_pthread.dylib __pthread_wqthread
17 libsystem_pthread.dylib _start_wqthread

Steps to reproduce

We haven't pinned down steps to reproduce yet. We'll update this ticket when we find out more.

Environment

• Bugsnag version: 6.1.2
• CocoaPods version: N/A
• Carthage version (if any): N/A
• iOS/tvOS/macOS version(s): 11.4.1 to 12.4.8. None on iOS 13 or 14 so far.
• Simulator or physical device: Physical Device
• Xcode version: Xcode 11.5 (11E608c)
• Swift version (if applicable): Apple Swift version 5.2.4 (swiftlang-1103.0.32.9 clang-1103.0.32.53)

[steve-nester-uk]

@jpsim thanks for raising the issue, we have seen similar (but not exactly the same) issues before that was fixed in 6.1.0 by adding validation of configuration input. I'm wondering if there was a case that was missed (of course it's also possible that is unrelated) - could you also provide snippets of your bugsnag configuration?

[jpsim]

Is there a private channel where I could share that information with you?

[steve-nester-uk]

@jpsim of course, please email [email protected] and we'll take a look.

[jpsim]

Sent an email. Thanks!

[xljones]

Hey @jpsim, a fix for this was released in https://github.com/bugsnag/bugsnag-cocoa/releases/tag/v6.1.5, under PR #807