Why does Call to undefined method app\models\AdduserForm::getDb() Yii2 error pop up?

Question

Yii

Hello. When I use this code in the controller
if($model->validate()){
\Yii::$app->session->setFlash('success', 'Data sent');
}else{
\Yii::$app->session->setFlash('error', 'Data error');
}
That the error gets out. Call to undefined method app\models\AdduserForm::getDb(). The error appears on $model->validate() .
Please tell me how to fix this?