Editor crash when enabling Distance Field AO Visualization in the Forward Renderer

MachineId:7D8A1A304BE9658328C158A3D14CC774
EpicAccountId:7c6293d6bf1940c0bc89e1494c5ba9d7

Assertion failed: IsValidRef(GBufferResourcesUniformBuffer) [File:d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\PostProcess/SceneRenderTargets.h] [Line: 412] 
GBuffer required but not available. Failure often caused by incorrect custom code use in a post processing material.


UE4Editor_Core!FDebug::AssertFailed() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:332]
UE4Editor_Renderer!FSceneRenderTargets::GetGBufferResourcesUniformBuffer() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\postprocess\scenerendertargets.h:414]
UE4Editor_Renderer!FDeferredPixelShaderParameters::Set<FRHIPixelShader * __ptr64,FRHICommandList>() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\postprocess\scenerendertargets.cpp:2493]
UE4Editor_Renderer!ComputeDistanceFieldNormal() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\distancefieldsurfacecachelighting.cpp:1053]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::RenderDistanceFieldLighting() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\distancefieldsurfacecachelighting.cpp:3121]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::Render() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:1213]
UE4Editor_Renderer!RenderViewFamily_RenderThread() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\renderer\private\scenerendering.cpp:1649]
UE4Editor_Renderer!TGraphTask<`FRendererModule::BeginRenderingViewFamily'::`21'::EURCMacro_FDrawSceneCommand>::ExecuteTask() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\public\async\taskgraphinterfaces.h:868]
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\async\taskgraph.cpp:932]
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilQuit() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\async\taskgraph.cpp:679]
UE4Editor_RenderCore!RenderingThreadMain() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\rendercore\private\renderingthread.cpp:320]
UE4Editor_RenderCore!FRenderingThread::Run() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\rendercore\private\renderingthread.cpp:454]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:74]