Corner case bug in Storage::updateContent()

$app['db']->update() only returns the number of affected rows as a return value.

\Doctrine\DBAL\Connection::update() calls \Doctrine\DBAL\Connection::executeUpdate() which only returns the above integer or throws a DBALException

**Doctrine API documentation**
Connection::update()
http://www.doctrine-project.org/api/dbal/2.4/source-class-Doctrine.DBAL.Connection.html#506-536

Connection::executeUpdate()
http://www.doctrine-project.org/api/dbal/2.4/source-class-Doctrine.DBAL.Connection.html#822-871