Error on gateway selection in plugin admin page

I have installed the WooCommerce Payment Discount – with WooCommerce 2.0.3.
I have found this erros: in the plugin admin page, I can’t see the Gateway selection; I see instead this error message Warning:
Invalid argument supplied for foreach() in \my url\wp-content\plugins\woocommerce-payment-discounts\wc-payment-discount.php on line 108

The line 108 on the cited page, is this:
` foreach ( get_option( ‘payment_gateway_order’ ) as $key => $value ) { ‘

Could please someone help me..

Thank you all very much!
Silvia

https://www.ads-software.com/extend/plugins/woocommerce-payment-discounts/