This is a common crash on Mac in the 4.16 release, and has occurred with low frequency since at least 4.11. Users have not provided any descriptions, so additional information is currently unknown. A log file is attached.
Callstack from Log
LogMaterial: Missing cached shader map for material ScotsPine_01_Branches_Mat, compiling. Cmd: TRANSACTION UNDO LogEditorTransaction: Undo Edit Mesh LogCrashTracker: LogMac: === Critical error: === SIGSEGV: invalid attempt to access memory at address 0x0 LogMac: SWindow::IsVisible() const Address = 0x10daa123 (filename not found) [in UE4Editor-SlateCore.dylib] PrepassWindowAndChildren(TSharedRef<SWindow, (ESPMode)0>) Address = 0x102f528a (filename not found) [in UE4Editor-Slate.dylib] FSlateApplication::DrawPrepass(TSharedPtr<SWindow, (ESPMode)0>) Address = 0x102f4e81 (filename not found) [in UE4Editor-Slate.dylib] FSlateApplication::PrivateDrawWindows(TSharedPtr<SWindow, (ESPMode)0>) Address = 0x102f0fc3 (filename not found) [in UE4Editor-Slate.dylib] FSlateApplication::DrawWindows() Address = 0x102f0a62 (filename not found) [in UE4Editor-Slate.dylib] FSlateApplication::TickApplication(ESlateTickType, float) Address = 0x102f9ffc (filename not found) [in UE4Editor-Slate.dylib] FSlateApplication::Tick(ESlateTickType) Address = 0x102f7e27 (filename not found) [in UE4Editor-Slate.dylib] FEngineLoop::Tick() Address = 0x9d0380c (filename not found) [in UE4Editor] GuardedMain(wchar_t const*) Address = 0x9d09e12 (filename not found) [in UE4Editor] -[UE4AppDelegate runGameThread:] Address = 0x9d1801a (filename not found) [in UE4Editor] -[FCocoaGameThread main] Address = 0x9fafa26 (filename not found) [in UE4Editor-Core.dylib] __NSThread__start__() Address = 0x773b030d (filename not found) [in Foundation] _pthread_body() Address = 0x8ac7aaab (filename not found) [in libsystem_pthread.dylib] _pthread_body() Address = 0x8ac7a9f7 (filename not found) [in libsystem_pthread.dylib] thread_start() Address = 0x8ac7a221 (filename not found) [in libsystem_pthread.dylib]
repro steps currently unknown. May be related to 'Undo'
SEGV_NOOP at 0x0 UE4Editor-SlateCore.dylib!SWindow::IsVisible() UE4Editor-Slate.dylib!PrepassWindowAndChildren(TSharedRef<SWindow,() UE4Editor-Slate.dylib!FSlateApplication::DrawPrepass(TSharedPtr<SWindow,() UE4Editor-Slate.dylib!FSlateApplication::PrivateDrawWindows(TSharedPtr<SWindow,() UE4Editor-Slate.dylib!FSlateApplication::DrawWindows() UE4Editor-Slate.dylib!FSlateApplication::TickApplication() UE4Editor-Slate.dylib!FSlateApplication::Tick() UE4Editor!FEngineLoop::Tick() UE4Editor!GuardedMain() UE4Editor!<Unknown> UE4Editor-Core.dylib!<Unknown> Foundation!Unknown() libsystem_pthread.dylib!<Unknown> libsystem_pthread.dylib!<Unknown> libsystem_pthread.dylib!<Unknown>
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-46421 in the post.