Fix : affichag des activités sans dates

<?php

/**

 * Created by PhpStorm.

 * User: jacksay

 * Date: 18/04/2018

 * Time: 13:39

 */

namespace Oscar\Entity;

use Oscar\Exception\OscarException;

use PHPUnit\Framework\TestCase;

class ActivityTest extends TestCase

{

    /**

     * @return ValidationPeriod

     */

    public function testDateStart(){

        $activity = new Activity();

        $dateStr = $activity->getDateStartStr();

        $this->assertEquals(null, $activity->getDateStart());

        $this->assertEquals("", $dateStr);

    }

}

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