Crash upon opening a level that is parented to a Custom Level Script

The attached project will crash whenever attempting to load the default map which is parented to a custom level script made by the user.

Note: This issue doesn't occur for all maps in the project. If you wish to convert to 4.8 without the project crashing on launch, change the default map to a blank map before converting to 4.8.

1. Download the project - [Link Removed]
2. Unzip the folder and right click the .uproject file to 'Switch Unreal Engine version' and select 4.8 (If you receive an error related to the Substance plugin, please delete the 'Plugins' folder and repeat this step)
3. Open the 'Test2.sln' file and, once it finishes loading, compile the project (ctrl+shift+b)
4. Open the project by double clicking the .uproject file
Result: The unreal engine stops responding while loading
Expected: The project loads without an issue

Fatal error: [Link Removed] [Line: 11]
Cast of Class /Script/Engine.BlueprintGeneratedClass to BlueprintGeneratedClass failed

KERNELBASE.dll

+ 0 bytes
UE4Editor-Core.dll!FOutputDeviceWindowsError::Serialize()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-Core.dll!FOutputDevice::Logf__VA()

+ 159 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-Core.dll!FDebug::AssertFailed()

+ 65 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-CoreUObject.dll!CastLogError()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-Engine.dll!CastChecked<UBlueprintGeneratedClass,UClass>()

+ 89 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-Engine.dll!UActorComponent::PostLoad()

+ 23 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-Engine.dll!ULightComponent::PostLoad()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-Engine.dll!UPointLightComponent::PostLoad()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-CoreUObject.dll!UObject::ConditionalPostLoad()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-CoreUObject.dll!EndLoad()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-CoreUObject.dll!LoadPackageInternal()

+ 5 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!UEditorEngine::Map_Load()

+ 29 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!UEditorEngine::HandleMapCommand()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!UEditorEngine::Exec()

+ 21 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!UUnrealEdEngine::Exec()

+ 17 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!FEditorFileUtils::LoadMap()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!FEditorFileUtils::LoadDefaultMapAtStartup()

+ 56 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!FUnrealEdMisc::OnInit()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor-UnrealEd.dll!EditorInit()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor.exe!GuardedMain()

+ 0 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor.exe!GuardedMainWrapper()

+ 5 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor.exe!WinMain()

+ 17 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\sou
UE4Editor.exe!__tmainCRTStartup()

+ 21 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]
kernel32.dll

+ 0 bytes
ntdll.dll

+ 0 bytes