fix bug in abstract/singletaskplaceevent due to doctrine update

src/Bundle/ChillTaskBundle/Entity/Task/SingleTaskPlaceEvent.php

@@ -31,6 +31,15 @@ use Doctrine\ORM\Mapping as ORM;
  */
 class SingleTaskPlaceEvent extends AbstractTaskPlaceEvent
 {
+    /**
+     * @var int
+     *
+     * @ORM\Column(name="id", type="integer")
+     * @ORM\Id
+     * @ORM\GeneratedValue(strategy="AUTO")
+     */
+    private $id;
+
     /**
      * @var SingleTask
      * @ORM\ManyToOne(