title: Symfony2 notice: Array to string conversion in Sonata Admin
body: <p>I'm using <strong>Sonata admin</strong> on <strong>Symfony 2.1.3</strong>. Now trying to add text input with google map.</p>
  
  <p>Added line in <code>configureFormFields()</code> function:</p>
  
  <pre><code>-&gt;add('coordinates', 'contentbundle_coordinates_map', array('required' =&gt; false,'attr'=&gt;array('class'=&gt;'mapCoordinate')))
  </code></pre>
  
  <p>registred in services and created template for this:</p>
  
  <pre><code>{% block contentbundle_coordinates_map_widget %}
      &lt;script type="text/javascript" src="https://maps.google.com/maps/api/js?sensor=true"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="{{ asset('js/add.scripts.js') }}"&gt;&lt;/script&gt;
      &lt;input type="text" {{ block('widget_attributes') }} {% if value is not empty %}value="{{ value }}" {% endif %}/&gt;
      &lt;div id="add_map" class="map" style="width:500px;height:300px;"&gt;&lt;/div&gt;
  {% endblock %}
  </code></pre>
  
  <p>Can see my field with map in admin content add page, but when I want to submit data getting:</p>
  
  <pre><code>Notice: Array to string conversion in D:\my_vendor_folder\doctrine\dbal\lib\Doctrine\DBAL\Statement.php line 103
  </code></pre>
  
  <p>If I change <strong>contentbundle_coordinates_map</strong> with <strong>null</strong>:</p>
  
  <pre><code>-&gt;add('coordinates', null, array('required' =&gt; false,'attr'=&gt;array('class'=&gt;'mapCoordinate')))
  </code></pre>
  
  <p>everything works.</p>
  
  <p>Where is the problem?</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>Form Type Class:</p>
  
  <pre><code>namespace Map\ContentBundle\Form\Type;
  
  use Symfony\Component\Form\AbstractType;
  use Symfony\Component\Form\FormBuilderInterface;
  
  class CoordinatesMapType extends AbstractType
  {
      /**
       * {@inheritdoc}
       */
      public function getName()
      {
          return 'contentbundle_coordinates_map';
      }
  }
  </code></pre>