[PLAT-6948] Fix crash in bsg_ksmachgetThreadQueueName

[nickdowell]

Goal

Fix a crash in dispatch_queue_get_label which appears to be due to an invalid dispatch_queue.

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000100000048
Exception Note:        EXC_CORPSE_NOTIFYVM

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libdispatch.dylib             0x0000000189abad00 dispatch_queue_get_label + 4
1   com.bugsnag.Bugsnag           0x0000000107e154ac bsg_ksmachgetThreadQueueName+ 324 (BSG_KSMach.c:324)
2   com.bugsnag.Bugsnag           0x0000000107e053e0 -[BugsnagThread initWithMachThread:backtraceAddresses:backtraceLength:errorReportingThread:index:] + 208 (BugsnagThread.m:326)

Changeset

The dispatch_queue is now probed to check that it points to a valid memory address before calling dispatch_queue_get_label.

Testing

Was not able to reproduce the crash.

Unit tests and E2E tests verify that bsg_ksmachgetThreadQueueName returns the expected name.

[github-actions]

Infer: No issues found 🎉

OCLint: No issues found 🎉

Bugsnag.framework binary size did not change - 1,134,024 bytes

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