common/services/entities/NewsletterMemberService.php
public function create( $model, $config = [] ) {

		if( empty( $model->siteId ) ) {

			$model->siteId = Yii::$app->core->site->id;
		}

		return parent::create( $model, $config );
 	}
public function create( $model, $config = [] ) {

		if( empty( $model->siteId ) ) {

			$model->siteId = Yii::$app->core->site->id;
		}

		return parent::create( $model, $config );
 	}
Create -------------