Custom Output node added to a Material Editor Crashes Editor

Adding a Custom Output node to a Material Graph crashes the editor.

Also Reproduced in Main Promotable-CL-2581018

[Link Removed]

1. Open the QAGame Editor
2. Create a New Material
3. Add a Custom Output Node

RESULTS: Crash

EXPECTED: No Crash

UE4Editor_Engine!UMaterialExpressionCustomOutput::GetFunctionName() materialexpressioncustomoutput.h:15
UE4Editor_Engine!FHLSLMaterialTranslator::Translate() hlslmaterialtranslator.h:501
UE4Editor_Engine!FMaterial::BeginCompileShaderMap() materialshared.cpp:1410
UE4Editor_Engine!FMaterial::CacheShaders() materialshared.cpp:1353
UE4Editor_Engine!FMaterial::CacheShaders() materialshared.cpp:1265
UE4Editor_Engine!UMaterial::CacheShadersForResources() material.cpp:1786
UE4Editor_Engine!UMaterial::CacheResourceShadersForRendering() material.cpp:1704
UE4Editor_Engine!UMaterial::PostEditChangeProperty() material.cpp:2604
UE4Editor_CoreUObject!UObject::PostEditChange() obj.cpp:284
UE4Editor_MaterialEditor!FMaterialEditor::UpdatePreviewMaterial() materialeditor.cpp:1242
UE4Editor_MaterialEditor!FMaterialEditor::CreateNewMaterialExpression() materialeditor.cpp:2982
UE4Editor_MaterialEditor!FMaterialEditorUtilities::CreateNewMaterialExpression() materialeditorutilities.cpp:34
UE4Editor_UnrealEd!FMaterialGraphSchemaAction_NewNode::PerformAction() materialgraphschema.cpp:36
UE4Editor_Engine!FEdGraphSchemaAction::PerformAction() edgraphschema.h:131
UE4Editor_GraphEditor!SGraphEditorActionMenu::OnActionSelected() sgrapheditoractionmenu.cpp:82
UE4Editor_GraphEditor!TBaseSPMethodDelegateInstance<0,SGraphEditorActionMenu,0,TTypeWrapper<void> __cdecl() delegateinstancesimpl_variadics.inl:282
UE4Editor_GraphEditor!SGraphActionMenu::HandleSelection() sgraphactionmenu.cpp:1315
UE4Editor_GraphEditor!SGraphActionMenu::OnItemSelected() sgraphactionmenu.cpp:1138
UE4Editor_GraphEditor!TBaseSPMethodDelegateInstance<0,SGraphActionMenu,0,TTypeWrapper<void> __cdecl() delegateinstancesimpl_variadics.inl:282
UE4Editor_GraphEditor!TBaseSPMethodDelegateInstance<0,SGraphActionMenu,0,void __cdecl() delegateinstancesimpl_variadics.inl:388
UE4Editor_GraphEditor!TBaseDelegate<void,TSharedPtr<FGraphActionNode,0>,enum ESelectInfo::Type>::ExecuteIfBound() delegatesignatureimpl_variadics.inl:519
UE4Editor_GraphEditor!SListView<TSharedPtr<FGraphActionNode,0> >::Private_SignalSelectionChanged() slistview.h:609
UE4Editor_GraphEditor!STableRow<TSharedPtr<FGraphActionNode,0> >::OnMouseButtonUp() stablerow.h:437
UE4Editor_Slate!<lambda_de96dc3471181973108233c6db1f9843>::operator() slateapplication.cpp:4311
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_de96dc3471181973108233c6db1f9843> >() slateapplication.cpp:212
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() slateapplication.cpp:4314
UE4Editor_Slate!FSlateApplication::OnMouseUp() slateapplication.cpp:4274
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1406
UE4Editor_Core!FWindowsApplication::DeferMessage() windowsapplication.cpp:1711
UE4Editor_Core!FWindowsApplication::ProcessMessage() windowsapplication.cpp:706
UE4Editor_Core!FWindowsApplication::AppWndProc() windowsapplication.cpp:628
user32!<Unknown>
user32!<Unknown>
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:792
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2340
UE4Editor!GuardedMain() launch.cpp:142
UE4Editor!GuardedMainWrapper() launchwindows.cpp:126
UE4Editor!WinMain() launchwindows.cpp:200