Description

The editor crashes when adding an actor to the level that contains a widget component (the class has to have been set (if the class is set to none the crash will not occur)) and the setting "Support Material Layers" has been set to true.

Steps to Reproduce
  1. Open the editor
  2. Set Support Material Layers to true (can be found in the project settings)
  3. Restart the editor
  4. Create a widget blueprint
  5. Create an actor blueprint
  6. Add a widget component to the newly created actor blueprint
  7. Set the class for the widget component to the widget blueprint that was created
  8. Save and compile
  9. Add the actor to the scene

Result: The editor will crash
Expected: The actor would be added to the scene without issue

Callstack
{no format}

UE4Editor_Engine!FMICReentranceGuard::FMICReentranceGuard() materialinstancesupport.h:39
UE4Editor_Engine!UMaterialInstance::GetVectorParameterDefaultValue() materialinstance.cpp:1990
UE4Editor_Engine!FMaterialUniformExpressionVectorParameter::GetNumberValue() materialuniformexpressions.h:95
UE4Editor_Engine!FUniformExpressionSet::CreateUniformBuffer() materialuniformexpressions.cpp:360
UE4Editor_Engine!FMaterialRenderProxy::EvaluateUniformExpressions() materialshared.cpp:1960
UE4Editor_Renderer!FMaterialShader::SetParametersInner<FRHIVertexShader * __ptr64>() shaderbaseclasses.cpp:217
UE4Editor_Renderer!FDepthDrawingPolicy::SetSharedState() depthrendering.cpp:411
UE4Editor_Renderer!FDepthDrawingPolicyFactory::DrawMesh() depthrendering.cpp:748
UE4Editor_Renderer!FDeferredShadingSceneRenderer::RenderPrePassViewDynamic() depthrendering.cpp:847
UE4Editor_Renderer!TGraphTask<FRenderPrepassDynamicDataThreadTask>::ExecuteTask() taskgraphinterfaces.h:829
UE4Editor_Core!FTaskThreadAnyThread::ProcessTasks() taskgraph.cpp:1022
UE4Editor_Core!FTaskThreadAnyThread::ProcessTasksUntilQuit() taskgraph.cpp:847
UE4Editor_Core!FTaskThreadAnyThread::Run() taskgraph.cpp:923
UE4Editor_Core!FRunnableThreadWin::Run() windowsrunnablethread.cpp:76 {no format}

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Fixed
ComponentRendering
Affects Versions4.21
Target Fix4.23
Fix Commit4628417
CreatedNov 13, 2018
ResolvedDec 4, 2018
UpdatedDec 4, 2018