Crash when Simulating in Editor after Painting Foliage

The engine crashes when simulating in the editor after painting foliage instances using the Foliage Tool.

An important thing to note is that this crash does not occur if you switch out of the 'Foliage' tool within the 'Modes' tab.

Regression?
Yes, this crash does not occur in the 4.13.2 release.

No crash: 4.13.2 - 3172292
Crash: 4.14 - 3195953
Crash: 4.15 - 3212501 (Dev-Main)

1. Create clean 4.14.0 C++ First person template (with starter content)

2. Put any mesh into foliage tool

3. Paint foliage with a few clicks

4. Press Simulate
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Also repros trying to enter foliage, landscape or mesh paint editor modes while Simulate is running.

UE4Editor_FoliageEdit!FEdModeFoliage::MouseMove() foliageedmode.cpp:818
UE4Editor_UnrealEd!FEditorModeTools::MouseMove() editormodemanager.cpp:760
UE4Editor_UnrealEd!FEditorViewportClient::MouseMove() editorviewportclient.cpp:4772
UE4Editor_Engine!FSceneViewport::OnMouseMove() sceneviewport.cpp:634
UE4Editor_Slate!SViewport::OnMouseMove() sviewport.cpp:206
UE4Editor_Slate!<lambda_76908516b038c565f6664336590b056a>::operator() slateapplication.cpp:5284
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_76908516b038c565f6664336590b056a> >() slateapplication.cpp:215
UE4Editor_Slate!FSlateApplication::RoutePointerMoveEvent() slateapplication.cpp:5274
UE4Editor_Slate!FSlateApplication::ProcessMouseMoveEvent() slateapplication.cpp:5653
UE4Editor_Slate!FSlateApplication::OnMouseMove() slateapplication.cpp:5592
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1693
UE4Editor_Core!FWindowsApplication::DeferMessage() windowsapplication.cpp:2071
UE4Editor_Core!FWindowsApplication::ProcessMessage() windowsapplication.cpp:814
UE4Editor_Core!FWindowsApplication::AppWndProc() windowsapplication.cpp:678
user32!<Unknown>
user32!<Unknown>
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:951
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2811
UE4Editor!GuardedMain() launch.cpp:152
UE4Editor!GuardedMainWrapper() launchwindows.cpp:126
UE4Editor!WinMain() launchwindows.cpp:202
UE4Editor!__scrt_common_main_seh() exe_common.inl:264
kernel32!<Unknown>
ntdll!<Unknown>