Crash during macOS installation

[Tor Arne Vestbø]

Thread 34 Queue : com.metacognitive.Microverse.VirtualMachineController (serial)
#0	0x00000001c3aa81f8 in dispatch thunk of AnySubscriberBase.receive(_:) ()
#1	0x00000001c6081a40 in closure #1 in NSObject.KVOSubscription.init<τ_0_0>(_:_:_:_:) ()
#2	0x00000001c6082e38 in partial apply for thunk for @escaping @callee_guaranteed (@guaranteed τ_0_0, @in_guaranteed NSKeyValueObservedChange<τ_0_1>) -> () ()
#3	0x00000001c60337b0 in closure #1 in _KeyValueCodingAndObserving.observe<τ_0_0>(_:options:changeHandler:) ()
#4	0x00000001c6033430 in specialized NSKeyValueObservation.Helper._swizzle_me_observeValue(forKeyPath:of:change:context:) ()
#5	0x00000001c6084180 in @objc NSKeyValueObservation.Helper._swizzle_me_observeValue(forKeyPath:of:change:context:) ()
#6	0x00000001b56a95dc in NSKeyValueNotifyObserver ()
#7	0x00000001b5775de0 in NSKeyValueDidChange ()
#8	0x00000001b5828b90 in NSKeyValueDidChangeWithPerThreadPendingNotifications ()
#9	0x00000001b482ae60 in __NSARRAY_IS_CALLING_OUT_TO_A_BLOCK__ ()
#10	0x00000001b482ae0c in -[__NSArrayM enumerateObjectsWithOptions:usingBlock:] ()
#11	0x00000001b56c61b4 in -[NSProgress _setValueForKeys:settingBlock:] ()
#12	0x00000001b56cb55c in -[NSProgress setCompletedUnitCount:] ()
#13	0x00000002180fee18 in void Base::DispatchQueue::async<-[VZMacOSInstaller reportProgress:]::$_3>(-[VZMacOSInstaller reportProgress:]::$_3&&)::'lambda'(void*)::__invoke(void*) ()
#14	0x0000000100b89e48 in _dispatch_client_callout ()
#15	0x0000000100b93168 in _dispatch_lane_serial_drain ()
#16	0x0000000100b9421c in _dispatch_lane_invoke ()
#17	0x0000000100ba3b04 in _dispatch_workloop_worker_thread ()
#18	0x0000000100aabfdc in _pthread_wqthread ()
Enqueued from com.apple.virtualization.installer-messenger (Thread 32) Queue : com.apple.virtualization.installer-messenger (serial)
#0	0x0000000100b8f538 in dispatch_async_f ()
#1	0x00000002180f7614 in VzInstallation::InstallerMessenger::handle_send_progress(unsigned int) ()
#2	0x00000002180f7300 in std::__1::__function::__func<VzShared::Messenger::Handler::Handler<VzInstallation::InstallerMessenger, unsigned int>(VzInstallation::InstallerMessenger&, void (VzInstallation::InstallerMessenger::*)(unsigned int))::'lambda'(Base::Xpc::Dictionary const&, Base::Xpc::Object), std::__1::allocator<VzShared::Messenger::Handler::Handler<VzInstallation::InstallerMessenger, unsigned int>(VzInstallation::InstallerMessenger&, void (VzInstallation::InstallerMessenger::*)(unsigned int))::'lambda'(Base::Xpc::Dictionary const&, Base::Xpc::Object)>, bool (Base::Xpc::Dictionary const&, Base::Xpc::Object)>::operator()(Base::Xpc::Dictionary const&, Base::Xpc::Object&&) ()
#3	0x00000002180ab604 in VzShared::Messenger::dispatch(Base::Xpc::Dictionary const&) ()
#4	0x00000002180f65a8 in invocation function for block in VzInstallation::InstallerMessenger::InstallerMessenger() ()
#5	0x00000001b44bf1e8 in _xpc_connection_call_event_handler ()
#6	0x00000001b44bdc08 in _xpc_connection_mach_event ()
#7	0x0000000100b89f08 in _dispatch_client_callout4 ()
#8	0x0000000100bada7c in _dispatch_mach_msg_invoke ()
#9	0x0000000100b92f0c in _dispatch_lane_serial_drain ()
#10	0x0000000100baf23c in _dispatch_mach_invoke ()
#11	0x0000000100b92f0c in _dispatch_lane_serial_drain ()
#12	0x0000000100b9421c in _dispatch_lane_invoke ()
#13	0x0000000100ba3b04 in _dispatch_workloop_worker_thread ()
#14	0x0000000100aabfdc in _pthread_wqthread ()
#15	0x0000000100ab3c78 in start_wqthread ()

[Justin Spahr-Summers]

Reproduced in testing just now. Looking into it.