title: EasyAdmin: "Unable to transform value for property path XY: Expected a string."
body: <p>When clicking the "Edit" link in EasyAdmin's list view of an entity that contains a field with <code>type="date"</code>, I'm getting this error message:</p>
  
  <blockquote>
    <p>Unable to transform value for property path "birthday": Expected a string.</p>
  </blockquote>
  
  <p>I have this in my entity:</p>
  
  <pre><code>/**
   * @ORM\Column(type="date")
   * @Assert\NotBlank()
   * @Assert\Date()
   */
  private $birthday;
  </code></pre>