file_widget errors out in a collection

[ghost]

bootstrap.twig.html:159

<input type="file" {{ block('widget_attributes') }} {% if value is not empty %}value="{{ value }}" {% endif %}>

should be something like

<input type="file" {{ block('widget_attributes') }}>

value is the file object.

simple example:

  $builder->add('imgs', 'collection', array(
        'type' => new FileType(),
        'data' => [
            new File(),
            new File(),
        ]
    ));

An exception has been thrown during the rendering of a template ("Catchable Fatal Error: Object of class File could not be converted to string in.. 159 etc