The given model has already started the "default_workflow" process - php

Question

I am building an entity listener in an application based on symfony 2.7. It will apply a tag to a video whenever the video's owning group changes.
My listener looks like this so far:
public function preUpdate($video, $args)
{
$changeSet = $args->getEntityChangeSet();
if(!array_key_exists('ownerGroup', $changeSet )){
return;
}
$oldGroupObj = $changeSet['ownerGroup'][0];
$oldGroupName = $oldGroupObj->getName();
//die($oldGroupName); //Gives us a valid group name string.
$tagRepository = $args->getEntityManager()->getRepository('AppBundle:Tag');
$tag = $tagRepository->findOneBy( ['title' => 'migrated' . $oldGroupName] );
if( $tag === null ){
$tag = new Tag;
$tag->setTitle('migrated' . $oldGroupName);
}
$video->addTag($tag);
}
The problem is that last line. When I run it, it causes this exception:
The given model has already started the "default_workflow" process.
What does this exception mean, and how can I save the new tag to my video when the owning group changes?

Answer 1

Trully, I have not develop application with symfony. But after read some documentation symfony, for your case exception The given model has already started the "default_workflow" process, interested at "Process Component", focused at Running Function (mustRun()), except that it will throw a ProcessFailedException if the process couldn't be executed successfully.
So, Globally, do not just focussed at your "function preUpdate", but all-of-your-big-code-symfony, because that exception "open from" The Process-Of-Your-Application