Running reflect.ValueOf(X) where X is a nil interface will return
a zero Value. We cannot get the type (because no concrete type is
known) and cannot check if the Value is nil later on due to the way
reflect.Value works. So we should handle this case by immediately
returning nil. We cannot type-assert a nil interface to another
interface type (as no concrete type is assigned), so we must add
another check to see if the returned interface is nil.
