this should be wrapped in an if statement. only if $invoke is not INVOKE_NONE we should call the invoker.

i guess the reason why orm repeats this code all over is to avoid creating the event argument objects when not needed. i tend to follow their example for performance reason. its not that heavy. 
```php
// if not available already $classmeta = ...
if ($invoke = $this->eventListenersInvoker->getSubscribedSystems(...) {
    $this->eventListenersInvoker->invoke( ... new LifecycleEventArgs ...)
}
```