[CrashReport] Assertion on Mac: Could not create a libwebsocket - FNetworkFileServerHttp::Init()

LogFileServer:Warning: Unreal Network Http File Server starting up...
LogMac:Error: appError called: Assertion failed: Assertion failed:  [File:/Users/build/Build/++UE4+Release-4.16+Compile/Sync/Engine/Source/Runtime/NetworkFileSystem/Private/NetworkFileServerHttp.cpp] [Line: 159] 
 Could not create a libwebsocket content for port : 41898

LogMac: === Critical error: ===
SIGSEGV: invalid attempt to access memory at address 0x3

LogMac: FGenericPlatformMisc::RaiseException(unsigned int) Address = 0x37d7f1b  (filename not found) [in UE4Editor-Core.dylib]
FOutputDeviceMacError::Serialize(wchar_t const*, ELogVerbosity::Type, FName const&) Address = 0x39d3d7f  (filename not found) [in UE4Editor-Core.dylib]
FOutputDevice::Logf(wchar_t const*, ...) Address = 0x3ab488d  (filename not found) [in UE4Editor-Core.dylib]
FDebug::AssertFailed(char const*, char const*, int, wchar_t const*, ...) Address = 0x3a1aafe  (filename not found) [in UE4Editor-Core.dylib]
FNetworkFileServerHttp::Init() Address = 0x1870c6a2 (filename not found) [in UE4Editor-NetworkFileSystem.dylib]
FRunnableThreadPThread::Run() Address = 0x3859458  (filename not found) [in UE4Editor-Core.dylib]
FRunnableThreadPThread::_ThreadProc(void*) Address = 0x38155f0  (filename not found) [in UE4Editor-Core.dylib]
_pthread_body() Address = 0xcef0493b (filename not found) [in libsystem_pthread.dylib]
_pthread_body() Address = 0xcef04887 (filename not found) [in libsystem_pthread.dylib]
thread_start() Address = 0xcef0408d (filename not found) [in libsystem_pthread.dylib]

SEGV_MAPERR at 0x3

UE4Editor-NetworkFileSystem.dylib!FNetworkFileServerHttp::Init() 
UE4Editor-Core.dylib!FRunnableThreadPThread::Run() 
UE4Editor-Core.dylib!FRunnableThreadPThread::_ThreadProc() 
libsystem_pthread.dylib!<Unknown> 
libsystem_pthread.dylib!<Unknown> 
libsystem_pthread.dylib!<Unknown>