FIXIF: Using the Merge Blueprints feature crashes the editor

Using the Merge Blueprints feature crashes the editor.

This repro is for clicking between the error and warnings while merging, but the editor will generally crash if the Merge is finished or if any components are deleted from the merge viewport.

1. Create a 1st Person blueprint project
2. Create 3 actor class blueprints named bp001, bp002, & bp003
3. Open bp001 & add a Box shape component
4. Open bp001 & add a Sphere shape component
5. Open bp001 & add a Capsule shape component
6. Compile & save all blueprints
7. Back in bp001, click File > Merge
8. Set the second and third blueprints to bp002 & bp003 (see screenshot 01)
9. Click 'Start Merge'
10. In the next view, click the dropdown arrow beside the red Components category
11. Click around on the different options "CONFLICT, Added Node, Added Node" (see screenshot 02)

Results: The editor will crash

Expected: To be able to click on these options to see the errors and warnings

MachineId:DE189244480D3CD0F8CA729A02DD38A6
EpicAccountId:75f47e038a8442f0af6c18e1f38eeb85

Access violation - code c0000005 (first/second chance not available)

UE4Editor_SlateCore!TWeakPtr<SWidget,0>::Pin() + 10 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\templates\sharedpointer.h:917]
UE4Editor_SlateCore!TSharedFromThis<SWidget,0>::AsShared() + 51 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\templates\sharedpointer.h:1001]
UE4Editor_Kismet!SKismetInspector::ShowDetailsForObjects() + 79 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismet\private\skismetinspector.cpp:363]
UE4Editor_Kismet!FSCSDiff::OnSCSEditorUpdateSelectionFromNodes() + 566 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismet\private\scsdiff.cpp:106]
UE4Editor_Kismet!TBaseRawMethodDelegateInstance<0,FSCSDiff,void __cdecl(TArray<TSharedPtr<FSCSEditorTreeNode,0>,FDefaultAllocator> const & __ptr64)>::ExecuteIfSafe() + 14 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:582]
UE4Editor_Kismet!SSCSEditor::OnTreeSelectionChanged() + 164 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismet\private\sscseditor.cpp:4855]
UE4Editor_Kismet!TBaseSPMethodDelegateInstance<0,SSCSEditor,0,TTypeWrapper<void> __cdecl(TSharedPtr<FSCSEditorTreeNode,0>,enum ESelectInfo::Type)>::Execute() + 106 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:282]
UE4Editor_Kismet!TBaseSPMethodDelegateInstance<0,SSCSEditor,0,void __cdecl(TSharedPtr<FSCSEditorTreeNode,0>,enum ESelectInfo::Type)>::ExecuteIfSafe() + 101 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:388]
UE4Editor_Kismet!TBaseDelegate<void,TSharedPtr<FSCSEditorTreeNode,0>,enum ESelectInfo::Type>::ExecuteIfBound() + 97 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegatesignatureimpl_variadics.inl:518]
UE4Editor_Kismet!SListView<TSharedPtr<FSCSEditorTreeNode,0> >::Private_SignalSelectionChanged() + 563 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\public\widgets\views\slistview.h:613]
UE4Editor_Kismet!SSCSEditor::HighlightTreeNode() + 566 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismet\private\sscseditor.cpp:3893]
UE4Editor_Kismet!FSCSDiff::HighlightProperty() + 213 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismet\private\scsdiff.cpp:47]
UE4Editor_Merge!SMergeTreeView::HighlightDifference() + 280 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\developer\merge\private\smergetreeview.cpp:272]
UE4Editor_Merge!<lambda_14e40743ec5e4b82d1d8071b4787faf5>::<helper_func_cdecl>() + 145 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\developer\merge\private\smergetreeview.cpp:210]
UE4Editor_Merge!TTupleImpl<TIntegerSequence<0,1,2>,`SMergeTreeView::Construct'::`25'::FSCSMergeEntry,SMergeTreeView * _ptr64,TBaseDelegate<void> >::ApplyAfter_ExplicitReturnType<void,void (_cdecl*const & __ptr64)(`SMergeTreeView::Construct'::`25'::FSCSMerg() + 176 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\tuple.h:79]
UE4Editor_Merge!TBaseStaticDelegateInstance<void __cdecl(void),`SMergeTreeView::Construct'::`25'::FSCSMergeEntry,SMergeTreeView * __ptr64,TBaseDelegate<void> >::ExecuteIfSafe() + 17 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:921]
UE4Editor_Kismet!<lambda_27a682e5807be2c10cdbb6dc02490d24>::<helper_func_cdecl>() + 62 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\kismet\private\diffutils.cpp:380]
UE4Editor_Kismet!TBaseStaticDelegateInstance<void __cdecl(TSharedPtr<FBlueprintDifferenceTreeEntry,0>,enum ESelectInfo::Type)>::ExecuteIfSafe() + 99 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:919]
UE4Editor_Kismet!TBaseDelegate<void,TSharedPtr<FBlueprintDifferenceTreeEntry,0>,enum ESelectInfo::Type>::ExecuteIfBound() + 97 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\public\delegates\delegatesignatureimpl_variadics.inl:518]
UE4Editor_Kismet!SListView<TSharedPtr<FBlueprintDifferenceTreeEntry,0> >::Private_SignalSelectionChanged() + 565 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\public\widgets\views\slistview.h:613]
UE4Editor_Kismet!STableRow<TSharedPtr<FBlueprintDifferenceTreeEntry,0> >::OnMouseButtonUp() + 1229 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\public\widgets\views\stablerow.h:437]
UE4Editor_Slate!<lambda_de96dc3471181973108233c6db1f9843>::operator()() + 188 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3985]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_de96dc3471181973108233c6db1f9843> >() + 215 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:202]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() + 601 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3988]
UE4Editor_Slate!FSlateApplication::OnMouseUp() + 294 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3949]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() + 3573 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:1373]
UE4Editor_Core!FWindowsApplication::DeferMessage() + 318 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:1669]
UE4Editor_Core!FWindowsApplication::ProcessMessage() + 4016 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:742]
UE4Editor_Core!FWindowsApplication::AppWndProc() + 114 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsapplication.cpp:604]
user32 + 105425 bytes
user32 + 104666 bytes
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() + 118 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:774]
UE4Editor!FEngineLoop::Tick() + 3737 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\launchengineloop.cpp:2233]
UE4Editor!GuardedMain() + 1404 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]