The current lazy loading code sets the initializer to null before the instance is initialized.

Code references RuntimeInstantiator (also in ProxyDumper):

public function instantiateProxy(ContainerInterface $container, Definition $definition, $id, $realInstantiator)
{
    return $this->factory->createProxy(
        $definition->getClass(),
        function (&$wrappedInstance, LazyLoadingInterface $proxy) use ($realInstantiator) {
            $proxy->setProxyInitializer(null);

            $wrappedInstance = call_user_func($realInstantiator);

            return true;
        }
    );
}

In cases where the constructor for this object throws an exception, subsequent method calls on this object will attempt to call a null object.

I feel that the ProxyInitializer should be set to null after the object is initialized. This way other method calls will attempt to initialize the object again if the exception was caught elsewhere.