Crash Undoing Create New Camera in Sequencer

If the user selects the "Create New Camera" button in a sequence, then uses undo, the editor crashes.

This issue does not occur in //UE4/Main @ 3046959

1. Create a new sequence
2. Select the "Create New Camera" button in the sequence
3. Ctrl + Z to undo
   RESULT: Crash

UE4Editor_CoreUObject!FWeakObjectPtr::IsValid() weakobjectptr.cpp:47
UE4Editor_Engine!ULevel::MarkLevelBoundsDirty() level.cpp:1313
UE4Editor_Engine!AActor::PostEditUndo() actoreditor.cpp:393
UE4Editor_UnrealEd!FTransaction::Apply() editortransaction.cpp:490
UE4Editor_UnrealEd!UTransBuffer::Undo() editortransaction.cpp:855
UE4Editor_UnrealEd!UEditorEngine::Exec_Transaction() editorserver.cpp:5080
UE4Editor_UnrealEd!UEditorEngine::Exec() editorserver.cpp:5526
UE4Editor_UnrealEd!UUnrealEdEngine::Exec() unrealedsrv.cpp:744
UE4Editor_MainFrame!FMainFrameActionCallbacks::ExecuteExecCommand() mainframeactions.cpp:920
UE4Editor_MainFrame!TBaseStaticDelegateInstance<void __cdecl() delegateinstancesimpl.h:1017
UE4Editor_Slate!FUICommandList::ConditionalProcessCommandBindings() uicommandlist.cpp:206
UE4Editor_Slate!FUICommandList::ProcessCommandBindings() uicommandlist.cpp:150
UE4Editor_MainFrame!FMainFrameActionCallbacks::OnUnhandledKeyDownEvent() mainframeactions.cpp:176
UE4Editor_MainFrame!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<FReply() tuple.h:115
UE4Editor_MainFrame!TBaseStaticDelegateInstance<FReply __cdecl() delegateinstancesimpl.h:948
UE4Editor_Slate!TBaseDelegate<FReply,FKeyEvent const & __ptr64>::Execute() delegatesignatureimpl.inl:521
UE4Editor_Slate!FSlateApplication::ProcessKeyDownEvent() slateapplication.cpp:4248
UE4Editor_Slate!FSlateApplication::OnKeyDown() slateapplication.cpp:4152
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1347
UE4Editor_Core!FWindowsApplication::DeferMessage() windowsapplication.cpp:1852
UE4Editor_Core!FWindowsApplication::ProcessMessage() windowsapplication.cpp:747
UE4Editor_Core!FWindowsApplication::AppWndProc() windowsapplication.cpp:669
user32!<Unknown>
user32!<Unknown>
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:905
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2771
UE4Editor!GuardedMain() launch.cpp:156
UE4Editor!GuardedMainWrapper() launchwindows.cpp:126
UE4Editor!WinMain() launchwindows.cpp:202
UE4Editor!__scrt_common_main_seh() exe_common.inl:264
kernel32!<Unknown>
ntdll!<Unknown>