Crash when closing the timeline tab inside UMG editor and reopening UMG editor

Crash when closing the timeline tab inside UMG editor and reopening UMG editor

Reported here:
https://udn.unrealengine.com/questions/307297/umg%E3%82%A8%E3%83%86%E3%82%A3%E3%82%BF%E8%B5%B7%E5%8B%95%E6%99%82%E3%81%ABstackoverflow%E3%82%92%E8%B5%B7%E3%81%93%E3%81%97%E3%81%BE%E3%81%99.html

1. Open a Widget blueprint in UMG Editor
2. Close the Timeline tab at the bottom of the window
   • [Image Removed]
3. Close UMG Editor
4. Open a Widget Blueprint in UMG Editor again
5. Observe crash

Access violation - code c0000005 (first/second chance not available)

UE4Editor_CoreUObject!FWeakObjectPtr::operator=() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\coreuobject\private\uobject\weakobjectptr.cpp:34]
UE4Editor_UMG!UWidgetAnimation::Initialize() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\umg\private\animation\widgetanimation.cpp:61]
UE4Editor_UMGEditor!FWidgetBlueprintEditor::ChangeViewedAnimation() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\umgeditor\private\widgetblueprinteditor.cpp:691]
UE4Editor_UMGEditor!SUMGAnimationList::OnEnteringDesignerMode() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\umgeditor\private\tabfactory\animationtabsummoner.cpp:326]
UE4Editor_UMGEditor!TBaseSPMethodDelegateInstance<0,SUMGAnimationList,0,TTypeWrapper<void> __cdecl(void)>::Execute() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:317]
UE4Editor_UMGEditor!TBaseSPMethodDelegateInstance<0,SUMGAnimationList,0,void __cdecl(void)>::ExecuteIfSafe() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:423]
UE4Editor_UMGEditor!TBaseMulticastDelegate<void>::Broadcast() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:921]
UE4Editor_UMGEditor!FWidgetDesignerApplicationMode::PostActivateMode() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\umgeditor\private\blueprintmodes\widgetdesignerapplicationmode.cpp:154]
UE4Editor_Kismet!FWorkflowCentricApplication::SetCurrentMode() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\kismet\private\workflowcentricapplication.cpp:72]
UE4Editor_Kismet!FBlueprintEditor::SetCurrentMode() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\kismet\private\blueprinteditor.cpp:1628]
UE4Editor_UMGEditor!FWidgetBlueprintEditor::RegisterApplicationModes() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\umgeditor\private\widgetblueprinteditor.cpp:162]
UE4Editor_Kismet!FBlueprintEditor::InitBlueprintEditor() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\kismet\private\blueprinteditor.cpp:1683]
UE4Editor_UMGEditor!FWidgetBlueprintEditor::InitWidgetBlueprintEditor() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\umgeditor\private\widgetblueprinteditor.cpp:101]
UE4Editor_UMGEditor!FAssetTypeActions_WidgetBlueprint::OpenAssetEditor() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\umgeditor\private\assettypeactions_widgetblueprint.cpp:33]
UE4Editor_UnrealEd!FAssetEditorManager::OpenEditorForAsset() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\unrealed\private\toolkits\asseteditormanager.cpp:338]
UE4Editor_UMGEditor!FAssetTypeActions_Base::AssetsActivated() [d:\build\++ue4+release-4.13+compile\sync\engine\source\developer\assettools\public\assettypeactions_base.h:41]
UE4Editor_ContentBrowser!SContentBrowser::OnAssetsActivated() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:1813]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,TTypeWrapper<void> __cdecl(TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type)>::Execute() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:317]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,void __cdecl(TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type)>::ExecuteIfSafe() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:424]
UE4Editor_ContentBrowser!TBaseDelegate<void,TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type>::ExecuteIfBound() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:608]
UE4Editor_ContentBrowser!SAssetView::OnListMouseButtonDoubleClick() [d:\build\++ue4+release-4.13+compile\sync\engine\source\editor\contentbrowser\private\sassetview.cpp:3555]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,TTypeWrapper<void> __cdecl(TSharedPtr<FAssetViewItem,0>)>::Execute() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:317]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,void __cdecl(TSharedPtr<FAssetViewItem,0>)>::ExecuteIfSafe() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:424]
UE4Editor_ContentBrowser!TBaseDelegate<void,TSharedPtr<FAssetViewItem,0> >::ExecuteIfBound() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:608]
UE4Editor_ContentBrowser!SListView<TSharedPtr<FAssetViewItem,0> >::Private_OnItemDoubleClicked() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\public\widgets\views\slistview.h:718]
UE4Editor_ContentBrowser!STableRow<TSharedPtr<FAssetViewItem,0> >::OnMouseButtonDoubleClick() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\public\widgets\views\stablerow.h:264]
UE4Editor_Slate!<lambda_eeb33fd1b480e3cad58a1531d90d2e14>::operator()() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5283]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_eeb33fd1b480e3cad58a1531d90d2e14> >() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:215]
UE4Editor_Slate!FSlateApplication::RoutePointerDoubleClickEvent() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5281]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonDoubleClickEvent() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5266]
UE4Editor_Slate!FSlateApplication::OnMouseDoubleClick() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5244]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:1588]
UE4Editor_Core!FWindowsApplication::DeferMessage() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:1930]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:747]
UE4Editor_Core!FWindowsApplication::AppWndProc() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:669]
user32
user32
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:905]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:2788]
UE4Editor!GuardedMain() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\launch\private\launch.cpp:156]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\build\++ue4+release-4.13+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
kernel32
ntdll