Unreal crash on STEP file datasmith import

Unreal Crash on .STEP file using the  Datasmith importer.

Works fine in 4.19.2 

Repro:

Import using datasmith CAD import

Importer setting use only geometry (see image attached)

Expected result: File open , catapillar is there 

Actual Result: CRASH

LoginId:e7b8dd8b44290f1cc89e2293f1ccd907
EpicAccountId:d75e404cff2a4cfd97abc0ccf186ac13

Assertion failed: MaterialIDs.Num() == (int)PartitionSizes.size() [Link Removed] [Line: 116]

UE4Editor_Core!FDebug::AssertFailed() [d:\perforce\deventerprise\engine\source\runtime\core\private\misc\assertionmacros.cpp:421]
UE4Editor_DatasmithCADImporter!FGPureMeshInterface::CreateMesh() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithcadimporter\source\datasmithcadimporter\private\gpuremeshinterface.cpp:118]
UE4Editor_DatasmithCADImporter!FDatasmithCADImporter::CreateStaticMesh() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithcadimporter\source\datasmithcadimporter\private\datasmithcadimporter.cpp:907]
UE4Editor_DatasmithCADImporter!UDatasmithCADImportFactory::ImportStaticMesh() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithcadimporter\source\datasmithcadimporter\private\datasmithcadimportfactory.cpp:285]
UE4Editor_DatasmithImporter!UDatasmithImportFactory::ImportStaticMeshes() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithimporter\source\datasmithimporter\private\datasmithimportfactory.cpp:960]
UE4Editor_DatasmithImporter!UDatasmithImportFactory::ImportDatasmithScene() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithimporter\source\datasmithimporter\private\datasmithimportfactory.cpp:267]
UE4Editor_DatasmithImporter!UDatasmithImportFactory::Import() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithimporter\source\datasmithimporter\private\datasmithimportfactory.cpp:790]
UE4Editor_DatasmithCADImporter!UDatasmithCADImportFactory::FactoryCreateFile() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithcadimporter\source\datasmithcadimporter\private\datasmithcadimportfactory.cpp:261]
UE4Editor_UnrealEd!UFactory::ImportObject() [d:\perforce\deventerprise\engine\source\editor\unrealed\private\factories\factory.cpp:170]
UE4Editor_DatasmithImporter!DatasmithImporterHelperInternal::ImportAssets() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithimporter\source\datasmithimporter\private\datasmithimporterhelper.cpp:81]
UE4Editor_DatasmithImporter!DatasmithImporterHelperInternal::Import() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithimporter\source\datasmithimporter\private\datasmithimporterhelper.cpp:146]
UE4Editor_DatasmithImporter!FDatasmithImporterHelper::ImportInternal() [d:\perforce\deventerprise\enterprise\plugins\editor\datasmithimporter\source\datasmithimporter\private\datasmithimporterhelper.cpp:216]
UE4Editor_DatasmithCADImporter!TBaseRawMethodDelegateInstance<0,FCADImporterModule,void __cdecl(void)>::ExecuteIfSafe() [d:\perforce\deventerprise\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:503]
UE4Editor_Slate!FUICommandList::ExecuteAction() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\commands\uicommandlist.cpp:97]
UE4Editor_Slate!SMenuEntryBlock::OnClicked() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:1028]
UE4Editor_Slate!SMenuEntryBlock::OnMenuItemButtonClicked() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:988]
UE4Editor_Slate!TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64>::operator()<>() [d:\perforce\deventerprise\engine\source\runtime\core\public\delegates\delegateinstanceinterface.h:156]
UE4Editor_Slate!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64> >() [d:\perforce\deventerprise\engine\source\runtime\core\public\templates\tuple.h:498]
UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SMenuEntryBlock,0,FReply __cdecl(void)>::Execute() [d:\perforce\deventerprise\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:269]
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() [d:\perforce\deventerprise\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:537]
UE4Editor_Slate!SButton::OnMouseButtonUp() [d:\perforce\deventerprise\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:282]
UE4Editor_Slate!SMenuEntryButton::OnMouseButtonUp() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:385]
UE4Editor_Slate!<lambda_1002768c627006711ef2f351a87ec0e7>::operator()() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5445]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_1002768c627006711ef2f351a87ec0e7> >() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:268]
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5434]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5932]
UE4Editor_Slate!FSlateApplication::OnMouseUp() [d:\perforce\deventerprise\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5912]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() [d:\perforce\deventerprise\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1726]
UE4Editor_ApplicationCore!FWindowsApplication::DeferMessage() [d:\perforce\deventerprise\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2172]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessMessage() [d:\perforce\deventerprise\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:889]
UE4Editor_ApplicationCore!FWindowsApplication::AppWndProc() [d:\perforce\deventerprise\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:726]
user32
user32
UE4Editor_ApplicationCore!FWindowsPlatformApplicationMisc::PumpMessages() [d:\perforce\deventerprise\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:129]
UE4Editor!FEngineLoop::Tick() [d:\perforce\deventerprise\engine\source\runtime\launch\private\launchengineloop.cpp:3282]
UE4Editor!GuardedMain() [d:\perforce\deventerprise\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\perforce\deventerprise\engine\source\runtime\launch\private\windows\launchwindows.cpp:144]
UE4Editor!WinMain() [d:\perforce\deventerprise\engine\source\runtime\launch\private\windows\launchwindows.cpp:223]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
kernel32
ntdll

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