loader.efi: Don't fail if we cannot find the current device

[manu]

Summary

While failing might seems ok, just warning the person and drop to
interact is better as he can debug stuff.

[imp]

I believe that this violates the UEFI Boot Manager Spec. If you fail for any reason, you have to return failure, not drop into the debugger...

So what brought you to want this change? What's the use case where this is useful? Perhaps there's a way we can detect when we're not participating in the boot manager protocol and just warn in that case.

[manu]

This is a hack, I'll keep it locally if I need it.