After adding MovieSceneObjectPropertyTrack from BP or Python, clicking the pull down of the added track occurs crash

When MovieSceneObjectPropertyTrack is added from BP or Python, PropertyClass of UMovieSceneObjectPropertyTrack becomes null, so it crashes with the following processing of SPropertyMenuAssetPicker :: Construct.

for(int32 i = 0; i < AllowedClasses.Num(); ++i)
{
   AssetPickerConfig.Filter.ClassNames.Add( AllowedClasses[i]->GetFName() );
}

MovieSceneObjectPropertyTrack PropertyClass needs to be editable from SequencerScripting or Ptyhon.

1. Open attacked repro proj
2. Run Editor Utility Widget and click button
3. Open LevelSequence and click pull down
4. crash

> UE4Editor-PropertyEditor.dll!SPropertyMenuAssetPicker::Construct(const SPropertyMenuAssetPicker::FArguments & InArgs) 行 117 C++
[インライン フレーム] UE4Editor-PropertyEditor.dll!RequiredArgs::T0RequiredArgs::CallConstruct(const TSharedRef<SPropertyMenuAssetPicker,0> &) 行 839 C++
[インライン フレーム] UE4Editor-PropertyEditor.dll!TDecl<SPropertyMenuAssetPicker,RequiredArgs::T0RequiredArgs>::operator<<=(const SPropertyMenuAssetPicker::FArguments &) 行 1098 C++
UE4Editor-PropertyEditor.dll!PropertyCustomizationHelpers::MakeAssetPickerWithMenu(const FAssetData & InitialObject, const bool AllowClear, const bool AllowCopyPaste, const TArray<UClass const *,FDefaultAllocator> & AllowedClasses, const TArray<UClass const *,FDefaultAllocator> & DisallowedClasses, const TArray<UFactory *,FDefaultAllocator> & NewAssetFactories, TBaseDelegate<bool,FAssetData const &> OnShouldFilterAsset, TBaseDelegate<void,FAssetData const &> OnSet, TBaseDelegate<void> OnClose) 行 285 C++
UE4Editor-PropertyEditor.dll!PropertyCustomizationHelpers::MakeAssetPickerWithMenu(const FAssetData & InitialObject, const bool AllowClear, const TArray<UClass const *,FDefaultAllocator> & AllowedClasses, const TArray<UClass const *,FDefaultAllocator> & DisallowedClasses, const TArray<UFactory *,FDefaultAllocator> & NewAssetFactories, TBaseDelegate<bool,FAssetData const &> OnShouldFilterAsset, TBaseDelegate<void,FAssetData const &> OnSet, TBaseDelegate<void> OnClose) 行 275 C++
UE4Editor-PropertyEditor.dll!SPropertyEditorAsset::OnGetMenuContent() 行 662 C++
[インライン フレーム] UE4Editor-PropertyEditor.dll!TMemberFunctionCaller<SPropertyEditorAsset,TSharedRef<SWidget,0> (__cdecl SPropertyEditorAsset::*)(void)>::operator()() 行 156 C++
[インライン フレーム] UE4Editor-PropertyEditor.dll!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter(TMemberFunctionCaller<SPropertyEditorAsset,TSharedRef<SWidget,0> (__cdecl SPropertyEditorAsset::*)(void)> &&) 行 498 C++
UE4Editor-PropertyEditor.dll!TBaseSPMethodDelegateInstance<0,SPropertyEditorAsset,0,TSharedRef<SWidget,0> __cdecl(void)>::Execute() 行 279 C++
[インライン フレーム] UE4Editor-Slate.dll!TBaseDelegate<TSharedRef<SWidget,0> >::Execute() 行 561 C++
UE4Editor-Slate.dll!SMenuAnchor::SetIsOpen(bool InIsOpen, const bool bFocusMenu, const int FocusUserIndex) 行 306 C++
UE4Editor-Slate.dll!SComboButton::OnButtonClicked() 行 86 C++
[インライン フレーム] UE4Editor-Slate.dll!TMemberFunctionCaller<SComboButton,FReply (__cdecl SComboButton::*)(void)>::operator()() 行 156 C++
[インライン フレーム] UE4Editor-Slate.dll!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter(TMemberFunctionCaller<SComboButton,FReply (__cdecl SComboButton::*)(void)> &&) 行 498 C++
UE4Editor-Slate.dll!TBaseSPMethodDelegateInstance<0,SComboButton,0,FReply __cdecl(void)>::Execute() 行 279 C++
[インライン フレーム] UE4Editor-Slate.dll!TBaseDelegate<FReply>::Execute() 行 561 C++
UE4Editor-Slate.dll!SButton::OnMouseButtonDown(const FGeometry & MyGeometry, const FPointerEvent & MouseEvent) 行 225 C++
[インライン フレーム] UE4Editor-Slate.dll!FSlateApplication::RoutePointerDownEvent::__l5::<lambda_6264868de66784e8427f79716494ab5b>::operator()(const FArrangedWidget) 行 5501 C++
UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_6264868de66784e8427f79716494ab5b> >(FSlateApplication * ThisApplication, FEventRouter::FBubblePolicy RoutingPolicy, FPointerEvent EventCopy, const FSlateApplication::RoutePointerDownEvent::__l5::<lambda_6264868de66784e8427f79716494ab5b> & Lambda) 行 271 C++
UE4Editor-Slate.dll!FSlateApplication::RoutePointerDownEvent(const FWidgetPath & WidgetsUnderPointer, const FPointerEvent & PointerEvent) 行 5487 C++
UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonDownEvent(const TSharedPtr<FGenericWindow,0> & PlatformWindow, const FPointerEvent & MouseEvent) 行 5440 C++
UE4Editor-Slate.dll!FSlateApplication::OnMouseDown(const TSharedPtr<FGenericWindow,0> & PlatformWindow, const EMouseButtons::Type Button, const FVector2D CursorPos) 行 5353 C++
UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage(const FDeferredWindowsMessage & DeferredMessage) 行 1850 C++
UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage(TSharedPtr<FWindowsWindow,0> & NativeWindow, HWND__ * InHWnd, unsigned int InMessage, unsigned __int64 InWParam, __int64 InLParam, int MouseX, int MouseY, unsigned int RawInputFlags) 行 2292 C++
UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage(HWND__ * hwnd, unsigned int msg, unsigned __int64 wParam, __int64 lParam) 行 1522 C++
UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc(HWND__ * hwnd, unsigned int msg, unsigned __int64 wParam, __int64 lParam) 行 772 C++
[外部コード]
[インライン フレーム] UE4Editor-ApplicationCore.dll!WinPumpMessages() 行 107 C++
UE4Editor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages(bool bFromMainLoop) 行 130 C++
UE4Editor.exe!FEngineLoop::Tick() 行 3882 C++
[インライン フレーム] UE4Editor.exe!EngineTick() 行 62 C++
UE4Editor.exe!GuardedMain(const wchar_t * CmdLine, HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, int nCmdShow) 行 168 C++
UE4Editor.exe!WinMain(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * __formal, int nCmdShow) 行 261 C++
[外部コード]