My problem is the following. I am using Sonata Admin with Symfony. In the Admin section, when I try to create an entity, nothing appears when I click on the add button (spelled "Ajouter"):

I get the following error: Call to a member function getName() on a non-object in the chrome console
Here's how my entities hierarchy is, I have three objects that are linked together in the following way:
Video ---OneToOne--> String ---OneToMany--> LocalizedString
Simply, I have one video that will have a title and this title will be translated. Here are my entities:
LocalizedString
OSC\UtilsBundle\Entity\LocalizedString:
    type: entity
    table: null
    repositoryClass: OSC\UtilsBundle\Entity\LocalizedStringRepository
    id:
        id:
            type: integer
            id: true
            generator:
                strategy: AUTO
    fields:
        locale:
            type: string
            length: '20'
        content:
            type: string
            length: 255
    manyToOne:
        parent:
            targetEntity: String
            mappedBy: localizedObjects
    lifecycleCallbacks: {  }
String
OSC\UtilsBundle\Entity\String:
    type: entity
    table: null
    repositoryClass: OSC\UtilsBundle\Entity\StringRepository
    id:
        id:
            type: integer
            id: true
            generator:
                strategy: AUTO
    oneToMany:
        localizedObjects:
            targetEntity: LocalizedString
            mappedBy: parent
            cascade: ["persist", "remove"]
    lifecycleCallbacks: {  }
Video
OSC\MySportBundle\Entity\Video:
    type: entity
    table: null
    repositoryClass: OSC\MySportBundle\Entity\VideoRepository
    id:
        id:
            type: integer
            id: true
            generator:
                strategy: AUTO
    oneToOne:
        title:
            targetEntity: OSC\UtilsBundle\Entity\String
            cascade: ["persist", "remove"]
    lifecycleCallbacks: {  }
So, I did this structure to facilitate the editing in SonataAdmin. If, through the admin dashboard, I want to edit a String, I can easily edit a string and translate it in many languages (this already works).
However, when I try to do that in the video admin, it seems that I cannot do inline editing (clicking the add button does not work) of the String object.
Here's the relevant code in video admin class:
$formMapper
        ->add('title', 'sonata_type_admin', array('delete' => false, 'btn_add' =>false), array(
            'edit' => 'inline',
            'inline' => 'table',
        ));
From what I have found, it looks like two imbricated forms are not possible ? Is there a way to circumvent that restriction ? Or maybe it is my design that is not too good ?
Edit1: It looks like there is a patch coming on github: https://github.com/sonata-project/SonataAdminBundle/pull/1971#issuecomment-58023124
If anyone knows how I can use it I would appreciate.