This crash happened when I saved a Blueprint and clicked Compile in rapid succession. Here is the stack trace:
MachineId:25334D8B554D9D49BD4BA4A53918171C
EpicAccountId:1ea6942a64614dbb89d9d32a796a128d
SEGV_MAPERR at 0x3
FGenericPlatformMisc::RaiseException(unsigned int) Address = 0x10a43adab (filename not found) [in UE4Editor-Core.dylib]
FOutputDeviceMacError::Serialize(wchar_t const*, ELogVerbosity::Type, FName const&) Address = 0x10a5f3378 (filename not found) [in UE4Editor-Core.dylib]
FOutputDevice::Logf(wchar_t const*, ...) Address = 0x10a6d0d17 (filename not found) [in UE4Editor-Core.dylib]
FDebug::AssertFailed(char const*, char const*, int, wchar_t const*, ...) Address = 0x10a64fb7e (filename not found) [in UE4Editor-Core.dylib]
StaticFindObject(UClass*, UObject*, wchar_t const*, bool) Address = 0x10b36f412 (filename not found) [in UE4Editor-CoreUObject.dylib]
FindPackage(UObject*, wchar_t const*) Address = 0x10b37431f (filename not found) [in UE4Editor-CoreUObject.dylib]
FPathContextMenu::ExecuteSaveFolder() Address = 0x1209ac1aa (filename not found) [in UE4Editor-ContentBrowser.dylib]
SContentBrowser::HandleSaveAllCurrentFolderCommand() const Address = 0x120b3d0a1 (filename not found) [in UE4Editor-ContentBrowser.dylib]
TBaseSPMethodDelegateInstance<true, SContentBrowser, (ESPMode)0, TTypeWrapper<void> ()>::Execute() const Address = 0x120c1988b (filename not found) [in UE4Editor-ContentBrowser.dylib]
TBaseSPMethodDelegateInstance<true, SContentBrowser, (ESPMode)0, void ()>::ExecuteIfSafe() const Address = 0x120c1992b (filename not found) [in UE4Editor-ContentBrowser.dylib]
FUICommandList::ConditionalProcessCommandBindings(FKey, bool, bool, bool, bool, bool) const Address = 0x10bd534ab (filename not found) [in UE4Editor-Slate.dylib]
FUICommandList::ProcessCommandBindings(FKeyEvent const&) const Address = 0x10bd52da7 (filename not found) [in UE4Editor-Slate.dylib]
SContentBrowser::OnKeyDown(FGeometry const&, FKeyEvent const&) Address = 0x120b46bb6 (filename not found) [in UE4Editor-ContentBrowser.dylib]
FSlateApplication::ProcessKeyDownEvent(FKeyEvent&) Address = 0x10bd1ae3f (filename not found) [in UE4Editor-Slate.dylib]
FSlateApplication::OnKeyDown(int, unsigned int, bool) Address = 0x10bd19853 (filename not found) [in UE4Editor-Slate.dylib]
FMacApplication::ProcessKeyDownEvent(FDeferredMacEvent const&, TSharedPtr<FMacWindow, (ESPMode)0>) Address = 0x10a59470b (filename not found) [in UE4Editor-Core.dylib]
FMacApplication::ProcessEvent(FDeferredMacEvent const&) Address = 0x10a58ced4 (filename not found) [in UE4Editor-Core.dylib]
FMacApplication::ProcessDeferredEvents(float) Address = 0x10a58ab0f (filename not found) [in UE4Editor-Core.dylib]
FSlateApplication::TickPlatform(float) Address = 0x10bcf0275 (filename not found) [in UE4Editor-Slate.dylib]
FSlateApplication::Tick() Address = 0x10bcef76b (filename not found) [in UE4Editor-Slate.dylib]
TickSlate(TSharedPtr<SWindow, (ESPMode)0>) Address = 0x10d616983 (filename not found) [in UE4Editor-UnrealEd.dylib]
FFeedbackContextEditor::ProgressReported(float, FText) Address = 0x10d617380 (filename not found) [in UE4Editor-UnrealEd.dylib]
FFeedbackContext::UpdateUI() Address = 0x10a6b733c (filename not found) [in UE4Editor-Core.dylib]
FSlowTask::EnterProgressFrame(float, FText) Address = 0x10a6fafbd (filename not found) [in UE4Editor-Core.dylib]
UPackage::Save(UPackage*, UObject*, EObjectFlags, wchar_t const*, FOutputDevice*, FLinkerLoad*, bool, bool, unsigned int, ITargetPlatform const*, FDateTime const&, bool) Address = 0x10b2cb046 (filename not found) [in UE4Editor-CoreUObject.dylib]
UEditorEngine::Save(UPackage*, UObject*, EObjectFlags, wchar_t const*, FOutputDevice*, FLinkerLoad*, bool, bool, unsigned int, ITargetPlatform const*, FDateTime const&, bool) Address = 0x10d2084a9 (filename not found) [in UE4Editor-UnrealEd.dylib]
UEditorEngine::SavePackage(UPackage*, UObject*, EObjectFlags, wchar_t const*, FOutputDevice*, FLinkerLoad*, bool, bool, unsigned int, ITargetPlatform const*, FDateTime const&, bool) Address = 0x10d209577 (filename not found) [in UE4Editor-UnrealEd.dylib]
UEditorEngine::Exec_Obj(wchar_t const*, FOutputDevice&) Address = 0x10d2b1c8f (filename not found) [in UE4Editor-UnrealEd.dylib]
UEditorEngine::Exec(UWorld*, wchar_t const*, FOutputDevice&) Address = 0x10d2ba33e (filename not found) [in UE4Editor-UnrealEd.dylib]
UUnrealEdEngine::Exec(UWorld*, wchar_t const*, FOutputDevice&) Address = 0x10de582e3 (filename not found) [in UE4Editor-UnrealEd.dylib]
InternalSavePackage(UPackage*, bool&, FOutputDevice&) Address = 0x10d63fb81 (filename not found) [in UE4Editor-UnrealEd.dylib]
FEditorFileUtils::PromptForCheckoutAndSave(TArray<UPackage*, FDefaultAllocator> const&, bool, bool, TArray<UPackage*, FDefaultAllocator>*, bool, bool) Address = 0x10d57f3c9 (filename not found) [in UE4Editor-UnrealEd.dylib]
ContentBrowserUtils::SavePackages(TArray<UPackage*, FDefaultAllocator> const&) Address = 0x12096af5b (filename not found) [in UE4Editor-ContentBrowser.dylib]
FPathContextMenu::ExecuteSaveFolder() Address = 0x1209ac3d6 (filename not found) [in UE4Editor-ContentBrowser.dylib]
SContentBrowser::HandleSaveAllCurrentFolderCommand() const Address = 0x120b3d0a1 (filename not found) [in UE4Editor-ContentBrowser.dylib]
TBaseSPMethodDelegateInstance<true, SContentBrowser, (ESPMode)0, TTypeWrapper<void> ()>::Execute() const Address = 0x120c1988b (filename not found) [in UE4Editor-ContentBrowser.dylib]
TBaseSPMethodDelegateInstance<true, SContentBrowser, (ESPMode)0, void ()>::ExecuteIfSafe() const Address = 0x120c1992b (filename not found) [in UE4Editor-ContentBrowser.dylib]
FUICommandList::ConditionalProcessCommandBindings(FKey, bool, bool, bool, bool, bool) const Address = 0x10bd534ab (filename not found) [in UE4Editor-Slate.dylib]
FUICommandList::ProcessCommandBindings(FKeyEvent const&) const Address = 0x10bd52da7 (filename not found) [in UE4Editor-Slate.dylib]
SContentBrowser::OnKeyDown(FGeometry const&, FKeyEvent const&) Address = 0x120b46bb6 (filename not found) [in UE4Editor-ContentBrowser.dylib]
FSlateApplication::ProcessKeyDownEvent(FKeyEvent&) Address = 0x10bd1ae3f (filename not found) [in UE4Editor-Slate.dylib]
FSlateApplication::OnKeyDown(int, unsigned int, bool) Address = 0x10bd19853 (filename not found) [in UE4Editor-Slate.dylib]
FMacApplication::ProcessKeyDownEvent(FDeferredMacEvent const&, TSharedPtr<FMacWindow, (ESPMode)0>) Address = 0x10a59470b (filename not found) [in UE4Editor-Core.dylib]
FMacApplication::ProcessEvent(FDeferredMacEvent const&) Address = 0x10a58ced4 (filename not found) [in UE4Editor-Core.dylib]
FMacApplication::ProcessDeferredEvents(float) Address = 0x10a58ab0f (filename not found) [in UE4Editor-Core.dylib]
FSlateApplication::TickPlatform(float) Address = 0x10bcf0275 (filename not found) [in UE4Editor-Slate.dylib]
FSlateApplication::Tick() Address = 0x10bcef76b (filename not found) [in UE4Editor-Slate.dylib]
FEngineLoop::Tick() Address = 0x10a355d65 (filename not found) [in UE4Editor]
GuardedMain(wchar_t const*) Address = 0x10a35bb72 (filename not found) [in UE4Editor]
-[UE4AppDelegate runGameThread:] Address = 0x10a36916c (filename not found) [in UE4Editor]
-[FCocoaGameThread main] Address = 0x10a582526 (filename not found) [in UE4Editor-Core.dylib]
Unknown() Address = 0x7fff8c569c6d (filename not found) [in Foundation]
_pthread_body Address = 0x7fffa033baab (filename not found) [in libsystem_pthread.dylib]
_pthread_body Address = 0x7fffa033b9f7 (filename not found) [in libsystem_pthread.dylib]
thread_start Address = 0x7fffa033b1fd (filename not found) [in libsystem_pthread.dylib]
UPDATE: I got this crash again and updated the stack trace above.