How to fix "Call to a member function isAttributeRequired() on null" error when opening linked tables form?

Question

Yii

Hello everybody! Tell me how to fix the problem, there are two interconnected tables Accept and Address. For understanding, data about the object is written to the Accept table, and data about the location of the object is written to the Address table. Saving data from the form to the database is fine, editing a new added record is also fine. The problem is that I need to edit previously added records in the Accept table, for which there is no information about the objects in the Address table yet, and when I open such an object, I get the following error:

Call to a member function isAttributeRequired() on null

update action

public function actionUpdate($id)
{
    $model = Accept::find()->where(['id'=>$id])->one();
    $address = Address::find()->where(['accept_id'=>$model->id])->one();

    if ($model->load(Yii::$app->request->post()) && $address->load(Yii::$app->request->post())) {
        if($model->save()){
            $address->accept_id = $model->id;
            if ($address->save()) {
                return $this->redirect(['view', 'id' => $model->id]);
            }
        }
    }
    return $this->render('update', compact('model', 'address'));
}