protected function checkConfig( \Aimeos\MShop\Service\Item\Iface $item )
	{
		$msg = '';
		$provider = $this->manager->getProvider( $item );
		$result = $provider->checkConfigBE( $item->getConfig() );

		foreach( $result as $key => $message )
		{
			if( $message !== null ) {
				$msg .= sprintf( "- %1\$s : %2\$s\n", $key, $message );
			}
		}

		if( $msg !== '' ) {
			throw new \Aimeos\Controller\ExtJS\Exception( "Invalid configuration:\n" . $msg );
		}
	}