Crash Occurs when changing the 'Max Metal Shader Standard To Target' option within iOS Project Settings

A crash occurs when setting the Max Metal Standard Shader version within the Project Settings for iOS. I tested on both Mac and PC and the crash occurs on both machines.

Regression?
No, this is not a regression as the feature was introduced in the 4.15 release.

1. Create new blank project targeted for Mobile/Tablet.
2. Go to Project Settings > iOS > Rendering
3. Change the Max Metal Standard Shader dropdown to either v 1.1 for v 1.2
4. Restart Project when Prompted.

Outcome The project crashes upon restarting the project.

Expected The new setting is applied appropriately and the user is able to restart their project without a crash.

UE4Editor_IOSPlatformEditor!FIOSTargetSettingsCustomization::SetShaderStandard()
UE4Editor_IOSPlatformEditor!FIOSTargetSettingsCustomization::UpdateShaderStandardWarning()
UE4Editor_IOSPlatformEditor!FIOSTargetSettingsCustomization::BuildPListSection()
UE4Editor_IOSPlatformEditor!FIOSTargetSettingsCustomization::CustomizeDetails()
UE4Editor_PropertyEditor!SDetailsViewBase::QueryCustomDetailLayout() sdetailsviewbase.cpp:992
UE4Editor_PropertyEditor!SDetailsViewBase::UpdateSinglePropertyMap() sdetailsviewbase.cpp:408
UE4Editor_PropertyEditor!SDetailsViewBase::UpdatePropertyMaps() sdetailsviewbase.cpp:373
UE4Editor_PropertyEditor!SDetailsView::PostSetObject() sdetailsview.cpp:796
UE4Editor_PropertyEditor!SDetailsView::SetObjectArrayPrivate() sdetailsview.cpp:584
UE4Editor_PropertyEditor!SDetailsView::SetObjects() sdetailsview.cpp:333
UE4Editor_SettingsEditor!SSettingsEditor::ReloadCategories() ssettingseditor.cpp:408
UE4Editor_SettingsEditor!SSettingsEditor::Construct() ssettingseditor.cpp:146
UE4Editor_SettingsEditor!TDecl<SSettingsEditor,RequiredArgs::T1RequiredArgs<TSharedRef<ISettingsEditorModel,0> const & __ptr64> >::operator<<=() declarativesyntaxsupport.h:1087
UE4Editor_SettingsEditor!FSettingsEditorModule::CreateEditor() settingseditormodule.cpp:157
UE4Editor_ProjectSettingsViewer!FProjectSettingsViewerModule::HandleSpawnSettingsTab() projectsettingsviewermodule.cpp:279
UE4Editor_ProjectSettingsViewer!TMemberFunctionCaller<FProjectSettingsViewerModule,TSharedRef<SDockTab,0>() delegateinstanceinterface.h:165
UE4Editor_ProjectSettingsViewer!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<FProjectSettingsViewerModule,TSharedRef<SDockTab,0>() tuple.h:134
UE4Editor_ProjectSettingsViewer!TBaseRawMethodDelegateInstance<0,FProjectSettingsViewerModule,TSharedRef<SDockTab,0> __cdecl() delegateinstancesimpl.h:556
UE4Editor_Slate!TBaseDelegate<TSharedRef<SDockTab,0>,FSpawnTabArgs const & __ptr64>::Execute() delegatesignatureimpl.inl:537
UE4Editor_Slate!FTabManager::SpawnTab() tabmanager.cpp:1413
UE4Editor_Slate!FTabManager::RestoreArea_Helper() tabmanager.cpp:1272
UE4Editor_Slate!FTabManager::RestoreSplitterContent() tabmanager.cpp:1387
UE4Editor_Slate!FTabManager::RestoreArea_Helper() tabmanager.cpp:1356
UE4Editor_Slate!FTabManager::RestoreArea() tabmanager.cpp:1248
UE4Editor_Slate!FTabManager::RestoreFrom() tabmanager.cpp:806
UE4Editor_MainFrame!FMainFrameModule::CreateDefaultMainFrame() mainframemodule.cpp:209
UE4Editor_UnrealEd!EditorInit() unrealedglobals.cpp:124
UE4Editor!GuardedMain() launch.cpp:150
UE4Editor!GuardedMainWrapper() launchwindows.cpp:134
UE4Editor!WinMain() launchwindows.cpp:210
UE4Editor!__scrt_common_main_seh() exe_common.inl:264
kernel32!<Unknown>
ntdll!<Unknown>