Crash if the number of spline points is less the one spline point currently selected

Spline components with "input spline points to construction script" enabled causes crash when selecting a spline point and reducing the total number of spline points below the selected spline.

Tested in: 4.23.1 CL#9631420,  4.25 CL#11574810

1. Download attached project and open Map1
2. Select the SplineActor placed in the level
3. Select the last spline of the actor
4. In the details panel, reduce the value of "Spline Points" to a number below the selected spline. 

Result: Crash

Expected: The spline points to be cleared with no crash

Assertion failed: LastKeyIndexSelected < Position.Points.Num() [Link Removed] [Line: 565]

UE4Editor_Core!FWindowsErrorOutputDevice::Serialize() [d:\build\++ue4\sync\engine\source\runtime\core\private\windows\windowserroroutputdevice.cpp:79]
UE4Editor_Core!FOutputDevice::LogfImpl() [d:\build\++ue4\sync\engine\source\runtime\core\private\misc\outputdevice.cpp:71]
UE4Editor_Core!AssertFailedImplV() [d:\build\++ue4\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:101]
UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [d:\build\++ue4\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:445]
UE4Editor_ComponentVisualizers!FSplineComponentVisualizer::GetWidgetLocation() [d:\build\++ue4\sync\engine\source\editor\componentvisualizers\private\splinecomponentvisualizer.cpp:565]
UE4Editor_UnrealEd!FComponentVisualizerManager::GetWidgetLocation() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\componentvisualizermanager.cpp:130]
UE4Editor_UnrealEd!FLevelEditorViewportClient::GetWidgetLocation() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\leveleditorviewport.cpp:3330]
UE4Editor_UnrealEd!FWidget::Render() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\unrealwidget.cpp:310]
UE4Editor_UnrealEd!FEditorViewportClient::Draw() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\editorviewportclient.cpp:3893]
UE4Editor_UnrealEd!FLevelEditorViewportClient::Draw() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\leveleditorviewport.cpp:4288]
UE4Editor_Renderer!FSceneRenderer::FSceneRenderer() [d:\build\++ue4\sync\engine\source\runtime\renderer\private\scenerendering.cpp:1902]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::FDeferredShadingSceneRenderer() [d:\build\++ue4\sync\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:206]
UE4Editor_Renderer!FSceneRenderer::CreateSceneRenderer() [d:\build\++ue4\sync\engine\source\runtime\renderer\private\scenerendering.cpp:2793]
UE4Editor_Renderer!FRendererModule::BeginRenderingViewFamily() [d:\build\++ue4\sync\engine\source\runtime\renderer\private\scenerendering.cpp:3435]
UE4Editor_UnrealEd!FEditorViewportClient::Draw() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\editorviewportclient.cpp:3751]
UE4Editor_Engine!FViewport::Draw() [d:\build\++ue4\sync\engine\source\runtime\engine\private\unrealclient.cpp:1579]
UE4Editor_UnrealEd!UEditorEngine::UpdateSingleViewportClient() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\editorengine.cpp:2065]
UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\editorengine.cpp:1770]
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\unrealedengine.cpp:407]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4\sync\engine\source\runtime\launch\private\launchengineloop.cpp:4257]
UE4Editor!GuardedMain() [d:\build\++ue4\sync\engine\source\runtime\launch\private\launch.cpp:173]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:147]
UE4Editor!WinMain() [d:\build\++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:279]
UE4Editor!__scrt_common_main_seh() [d:\agent\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll