Howto abort startup on fatal misconfiguration?

Development Programming & Scripting
1

I just renamed a property (HandControllerBluePrint), which blanked its value in the editor. This caused the project to crash at runtime. I had to figure that out by debugging.

I had a nullptr check but it’s a fatal misconfiguration:

LeftController = GetWorld()->SpawnActor<AHandController>(HandControllerBlueprint);
if (LeftController != nullptr) {
	LeftController->AttachToComponent(VRRoot, FAttachmentTransformRules::KeepRelativeTransform);
	LeftController->SetHand(EControllerHand::Left);
	LeftController->SetOwner(this); // FIX FOR 4.22
} else {
    // How to throw fatal error for designer here?
}

It crashes the editor which is a bummer.

I’d prefer a basic popup-alert-then-exit to a log message. Any suggestions? Thank you!