Crash when opening a blueprint that referenced a struct blueprint that no longer exists

If a user creates a struct blueprint then references it in another blueprint and then deletes the struct while the editor is closed, the referencing blueprint will crash when opened.

1. Create a new project
2. Create a new Blueprint Struct (Right click the content browser, blueprints -> structure)
3. Create a new blueprint of the actor class
4. In the new actor blueprint's event graph, add a 'Set Members in NewUserDefinedStruct' node
5. Drag off the 'Struct Ref' pin for this node and select 'Promote to Variable'
6. Save all and close the editor
7. Navigate to the project's content folder and delete the struct
8. Launch the editor and attempt to open the blueprint
9. Notice that the editor will crash

Assertion failed: Result != NULL [Link Removed] [Line: 101]

KERNELBASE.dll!UnknownFunction (0x000007fefd38aaad) + 0 bytes [UnknownFile:0]
UE4Editor-Core.dll!FOutputDeviceWindowsError::Serialize() (0x000007fee3a68074) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:95]
UE4Editor-Core.dll!FOutputDevice::Logf__VA() (0x000007fee38e7878) + 159 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\misc\outputdevice.cpp:144]
UE4Editor-Core.dll!FDebug::AssertFailed() (0x000007fee38c8b17) + 62 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\misc\outputdevice.cpp:224]
UE4Editor-Engine.dll!UEdGraphNode::FindPinChecked() (0x000007fed9ae5354) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\engine\private\edgraph\edgraphnode.cpp:102]
UE4Editor-BlueprintGraph.dll!UK2Node_SetFieldsInStruct::ValidateNodeDuringCompilation() (0x000007fee01b41af) + 64 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\blueprintgraph\private\k2node_setfieldsinstruct.cpp:98]
UE4Editor-KismetCompiler.dll!FKismetCompilerContext::CreateAndProcessUbergraph() (0x000007fee0da60a8) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismetcompiler\private\kismetcompiler.cpp:2752]
UE4Editor-KismetCompiler.dll!FKismetCompilerContext::CreateFunctionList() (0x000007fee0da8f35) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismetcompiler\private\kismetcompiler.cpp:3136]
UE4Editor-KismetCompiler.dll!FKismetCompilerContext::Compile() (0x000007fee0d9a82b) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismetcompiler\private\kismetcompiler.cpp:3389]
UE4Editor-KismetCompiler.dll!FKismet2CompilerModule::CompileBlueprintInner() (0x000007fee0d9da19) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismetcompiler\private\kismetcompilermodule.cpp:87]
UE4Editor-KismetCompiler.dll!FKismet2CompilerModule::CompileBlueprint() (0x000007fee0d9d2f1) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismetcompiler\private\kismetcompilermodule.cpp:139]
UE4Editor-UnrealEd.dll!FKismetEditorUtilities::CompileBlueprint() (0x000007fee18a79f2) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\unrealed\private\kismet2\kismet2.cpp:742]
UE4Editor-UnrealEd.dll!FBlueprintEditorUtils::RegenerateBlueprintClass() (0x000007fee18599d2) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\unrealed\private\kismet2\blueprinteditorutils.cpp:1255]
UE4Editor-CoreUObject.dll!ULinkerLoad::RegenerateBlueprintClass() (0x000007fee410ed77) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\blueprint\blueprintsupport.cpp:289]
UE4Editor-CoreUObject.dll!ULinkerLoad::FinalizeBlueprint() (0x000007fee40e4515) + 15 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\blueprint\blueprintsupport.cpp:1000]
UE4Editor-CoreUObject.dll!ULinkerLoad::Preload() (0x000007fee418da39) + 11 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:3019]
UE4Editor-CoreUObject.dll!ULinkerLoad::CreateExport() (0x000007fee41646d5) + 16 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:3611]
UE4Editor-CoreUObject.dll!ULinkerLoad::IndexToObject() (0x000007fee4182ac8) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:3809]
UE4Editor-CoreUObject.dll!ULinkerLoad::CreateExport() (0x000007fee4163db1) + 11 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:3334]
UE4Editor-CoreUObject.dll!ULinkerLoad::CreateExportAndPreload() (0x000007fee416497b) + 5 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:2520]
UE4Editor-CoreUObject.dll!ULinkerLoad::LoadAllObjects() (0x000007fee418505b) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:2628]
UE4Editor-CoreUObject.dll!LoadPackageInternal() (0x000007fee4237da9) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:894]
UE4Editor-CoreUObject.dll!ResolveName() (0x000007fee4240f2b) + 63 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:610]
UE4Editor-CoreUObject.dll!StaticLoadObject() (0x000007fee42463af) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:697]
UE4Editor-ContentBrowser.dll!FAssetData::GetAsset() (0x000007fed10bc587) + 62 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\assetregistry\public\assetdata.h:178]
UE4Editor-ContentBrowser.dll!SContentBrowser::OnAssetsActivated() (0x000007fed112193b) + 87 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:1576]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,TTypeWrapper<void> __cdecl(TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type)>::Execute() (0x000007fed109ab17) + 38 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:282]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,void __cdecl(TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type)>::ExecuteIfSafe() (0x000007fed10a60f7) + 14 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:388]
UE4Editor-ContentBrowser.dll!SAssetView::OnListMouseButtonDoubleClick() (0x000007fed112d337) + 42 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\contentbrowser\private\sassetview.cpp:3207]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,SAssetView,0,TTypeWrapper<void> __cdecl(TSharedPtr<FAssetViewItem,0>)>::Execute() (0x000007fed1099671) + 52 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:282]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,SAssetView,0,void __cdecl(TSharedPtr<FAssetViewItem,0>)>::ExecuteIfSafe() (0x000007fed10a531a) + 37 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:388]
UE4Editor-ContentBrowser.dll!TBaseDelegate<void,TSharedPtr<FAssetViewItem,0> >::ExecuteIfBound() (0x000007fed10a25b6) + 38 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegatesignatureimpl_variadics.inl:518]
UE4Editor-ContentBrowser.dll!SListView<TSharedPtr<FAssetViewItem,0> >::Private_OnItemDoubleClicked() (0x000007fed11431bf) + 41 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\public\widgets\views\slistview.h:693]
UE4Editor-ContentBrowser.dll!STableRow<TSharedPtr<FAssetViewItem,0> >::OnMouseButtonDoubleClick() (0x000007fed112d59f) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\public\widgets\views\stablerow.h:252]
UE4Editor-Slate.dll!<lambda_58ede244782f1e594383d45514e1d7c8>::operator()() (0x000007fee2f4d38e) + 9 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3918]
UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_58ede244782f1e594383d45514e1d7c8> >() (0x000007fee2f0774d) + 21 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:202]
UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonDoubleClickEvent() (0x000007fee2fb4507) + 90 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3919]
UE4Editor-Slate.dll!FSlateApplication::OnMouseDoubleClick() (0x000007fee2fa417b) + 19 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3900]
UE4Editor-Core.dll!FWindowsApplication::ProcessDeferredMessage() (0x000007fee39c37e8) + 32 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:1315]
UE4Editor-Core.dll!FWindowsApplication::DeferMessage() (0x000007fee39b5d2e) + 74 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:1669]
UE4Editor-Core.dll!FWindowsApplication::ProcessMessage() (0x000007fee39c4d50) + 41 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:742]
UE4Editor-Core.dll!FWindowsApplication::AppWndProc() (0x000007fee39b3192) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:604]
USER32.dll!UnknownFunction (0x00000000771c9bd1) + 0 bytes [UnknownFile:0]
USER32.dll!UnknownFunction (0x00000000771c98da) + 0 bytes [UnknownFile:0]
UE4Editor-Core.dll!FWindowsPlatformMisc::PumpMessages() (0x000007fee3a63ec6) + 48 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:774]
UE4Editor.exe!FEngineLoop::Tick() (0x000000013ff700a9) + 8 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\launchengineloop.cpp:2233]
UE4Editor.exe!GuardedMain() (0x000000013ff6267c) + 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor.exe!GuardedMainWrapper() (0x000000013ff626ea) + 5 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor.exe!WinMain() (0x000000013ff72219) + 17 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
UE4Editor.exe!__tmainCRTStartup() (0x000000013ff73159) + 21 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]
kernel32.dll!UnknownFunction (0x00000000772c59cd) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00000000773fb891) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00000000773fb891) + 0 bytes [UnknownFile:0]