[CrashReport] Crash on Mac due to uncaught exception 'NSRangeException' - NSCFConstantString characterAtIndex

LogMac: === Critical error: ===
SIGABRT: abort() called

LogMac: __pthread_kill() Address = 0xad4dbd42 (filename not found) [in libsystem_kernel.dylib]
abort() Address = 0xad441420 (filename not found) [in libsystem_c.dylib]
-[PLCrashReporter generateLiveReportWithThread:] Address = 0x1e30b3c  (filename not found) [in UE4Editor-Core.dylib]

__handleUncaughtException() Address = 0x97906019 (filename not found) [in CoreFoundation]
_objc_terminate() Address = 0xacace335 (filename not found) [in libobjc.A.dylib]
std::__terminate(void (*)()) Address = 0xabfbdd69 (filename not found) [in libc++abi.dylib]
__cxxabiv1::exception_cleanup_func(_Unwind_Reason_Code, _Unwind_Exception*) Address = 0xabfbd7de (filename not found) [in libc++abi.dylib]
objc_exception_throw() Address = 0xacacc303 (filename not found) [in libobjc.A.dylib]
+[NSException raise:format:] Address = 0x97905c55 (filename not found) [in CoreFoundation]
-[__NSCFString characterAtIndex:] Address = 0x97801396 (filename not found) [in CoreFoundation]
FMacApplication::ProcessKeyDownEvent(FDeferredMacEvent const&, TSharedPtr<FMacWindow, (ESPMode)0>) Address = 0x205c078  (filename not found) [in UE4Editor-Core.dylib]
FMacApplication::ProcessEvent(FDeferredMacEvent const&) Address = 0x2052131  (filename not found) [in UE4Editor-Core.dylib]
FMacApplication::ProcessDeferredEvents(float) Address = 0x204feaf  (filename not found) [in UE4Editor-Core.dylib]
FSlateApplication::TickPlatform(float) Address = 0x83939db  (filename not found) [in UE4Editor-Slate.dylib]
FSlateApplication::Tick(ESlateTickType) Address = 0x8392e14  (filename not found) [in UE4Editor-Slate.dylib]
FEngineLoop::Tick() Address = 0x1d9a80c  (filename not found) [in UE4Editor]
GuardedMain(wchar_t const*) Address = 0x1da0e12  (filename not found) [in UE4Editor]
-[UE4AppDelegate runGameThread:] Address = 0x1daf01a  (filename not found) [in UE4Editor]
-[FCocoaGameThread main] Address = 0x2047346  (filename not found) [in UE4Editor-Core.dylib]
__NSThread__start__() Address = 0x99240b3d (filename not found) [in Foundation]
_pthread_body() Address = 0xad5c693b (filename not found) [in libsystem_pthread.dylib]
_pthread_body() Address = 0xad5c6887 (filename not found) [in libsystem_pthread.dylib]
thread_start() Address = 0xad5c608d (filename not found) [in libsystem_pthread.dylib]

#0 at 0x7fffad4dbd42 *** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFConstantString characterAtIndex:]: Range or index out of bounds'

libsystem_kernel.dylib!<Unknown>
libsystem_c.dylib!<Unknown>
UE4Editor-Core.dylib!<Unknown>
???!Unknown()
CoreFoundation!<Unknown>
libobjc.A.dylib!_objc_terminate()
libc++abi.dylib!std::__terminate(void (*)()
libc++abi.dylib!__cxxabiv1::exception_cleanup_func()
libobjc.A.dylib!<Unknown>
CoreFoundation!<Unknown>
CoreFoundation!<Unknown>
UE4Editor-Core.dylib!FMacApplication::ProcessKeyDownEvent(FDeferredMacEvent const&, TSharedPtr<FMacWindow,()
UE4Editor-Core.dylib!FMacApplication::ProcessEvent()
UE4Editor-Core.dylib!FMacApplication::ProcessDeferredEvents()
UE4Editor-Slate.dylib!FSlateApplication::TickPlatform()
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>