Description

Undo, redo, undo after issuing a replace actor action causes the editor to crash.

Found on: //UE4/Release-4.13 CL-3078131

Crash reporter: [Link Removed]

Regression from //UE4/Release-4.12 CL-3053425 , will investigate range on request.
Does not reproduce in //UE4/Main CL-3078219.
Does not reproduce in //UE4/Dev-Blueprints CL-3078965.

Steps to Reproduce
  1. Open UE4Editor.exe QAGAME
  2. Place an instance of BP_Variable into the world
  3. Alt+Drag to duplicate BP_Variable
  4. Select both instances of BP_Variable
  5. Search for ContextMesh in the content browser
  6. Select it in the content browser
  7. Right click on one of the two instances of BP_Variable
  8. Replace Instances with ContextMesh
  9. Undo
  10. Redo
  11. Undo

Result: Crash

Callstack
MachineId:93621A354124D3DA0CD87BB8C7BF4324
EpicAccountId:a93319c1a68241d295f2574a4ba3da59

Assertion failed: Pair != nullptr [File:D:\Release-4.13\Engine\Source\Runtime\Core\Public\Containers\Map.h] [Line: 522] 



UE4Editor_Core!FDebug::AssertFailed() [d:\release-4.13\engine\source\runtime\core\private\misc\outputdevice.cpp:421]
UE4Editor_Engine!AActor::RerunConstructionScripts() [d:\release-4.13\engine\source\runtime\engine\private\actorconstruction.cpp:551]
UE4Editor_Engine!AActor::PostEditChangeProperty() [d:\release-4.13\engine\source\runtime\engine\private\actoreditor.cpp:105]
UE4Editor_CoreUObject!UObject::PostEditUndo() [d:\release-4.13\engine\source\runtime\coreuobject\private\uobject\obj.cpp:482]
UE4Editor_CoreUObject!UObject::PostEditUndo() [d:\release-4.13\engine\source\runtime\coreuobject\private\uobject\obj.cpp:486]
UE4Editor_Engine!AActor::PostEditUndo() [d:\release-4.13\engine\source\runtime\engine\private\actoreditor.cpp:445]
UE4Editor_UnrealEd!FTransaction::Apply() [d:\release-4.13\engine\source\editor\unrealed\private\editortransaction.cpp:488]
UE4Editor_UnrealEd!UTransBuffer::Undo() [d:\release-4.13\engine\source\editor\unrealed\private\editortransaction.cpp:855]
UE4Editor_UnrealEd!UEditorEngine::Exec_Transaction() [d:\release-4.13\engine\source\editor\unrealed\private\editorserver.cpp:5081]
UE4Editor_UnrealEd!UEditorEngine::Exec() [d:\release-4.13\engine\source\editor\unrealed\private\editorserver.cpp:5527]
UE4Editor_UnrealEd!UUnrealEdEngine::Exec() [d:\release-4.13\engine\source\editor\unrealed\private\unrealedsrv.cpp:624]
UE4Editor_MainFrame!FMainFrameActionCallbacks::ExecuteExecCommand() [d:\release-4.13\engine\source\editor\mainframe\private\frame\mainframeactions.cpp:925]
UE4Editor_MainFrame!TBaseStaticDelegateInstance<void __cdecl(void),FString>::ExecuteIfSafe() [d:\release-4.13\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:1017]
UE4Editor_Slate!FUICommandList::ConditionalProcessCommandBindings() [d:\release-4.13\engine\source\runtime\slate\private\framework\commands\uicommandlist.cpp:211]
UE4Editor_Slate!FUICommandList::ProcessCommandBindings() [d:\release-4.13\engine\source\runtime\slate\private\framework\commands\uicommandlist.cpp:155]
UE4Editor_MainFrame!FMainFrameActionCallbacks::OnUnhandledKeyDownEvent() [d:\release-4.13\engine\source\editor\mainframe\private\frame\mainframeactions.cpp:176]
UE4Editor_MainFrame!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<FReply (__cdecl*const & __ptr64)(FKeyEvent const & __ptr64),FKeyEvent const & __ptr64>() [d:\release-4.13\engine\source\runtime\core\public\delegates\tuple.h:115]
UE4Editor_MainFrame!TBaseStaticDelegateInstance<FReply __cdecl(FKeyEvent const & __ptr64)>::Execute() [d:\release-4.13\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:948]
UE4Editor_Slate!TBaseDelegate<FReply,FKeyEvent const & __ptr64>::Execute() [d:\release-4.13\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:521]
UE4Editor_Slate!FSlateApplication::ProcessKeyDownEvent() [d:\release-4.13\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4528]
UE4Editor_Slate!FSlateApplication::OnKeyDown() [d:\release-4.13\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4430]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [d:\release-4.13\engine\source\runtime\core\private\windows\windowsapplication.cpp:1419]
UE4Editor_Core!FWindowsApplication::DeferMessage() [d:\release-4.13\engine\source\runtime\core\private\windows\windowsapplication.cpp:1930]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [d:\release-4.13\engine\source\runtime\core\private\windows\windowsapplication.cpp:747]
UE4Editor_Core!FWindowsApplication::AppWndProc() [d:\release-4.13\engine\source\runtime\core\private\windows\windowsapplication.cpp:669]
user32
user32
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [d:\release-4.13\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:905]
UE4Editor!FEngineLoop::Tick() [d:\release-4.13\engine\source\runtime\launch\private\launchengineloop.cpp:2788]
UE4Editor!GuardedMain() [d:\release-4.13\engine\source\runtime\launch\private\launch.cpp:156]
UE4Editor!GuardedMainWrapper() [d:\release-4.13\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\release-4.13\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:255]
kernel32
ntdll

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Fixed
ComponentTools
Affects Versions4.13
Target Fix4.13
Fix Commit3086735
Main Commit3092051
Release Commit3086735
CreatedAug 4, 2016
ResolvedAug 11, 2016
UpdatedMay 2, 2018