Plugin Conflict Woocommerce

Hi! When plugin is active, i can’t finish checkout, because i have this error
http://prntscr.com/pdv3kr

When plugin if off, checkout work good. Can you help me?

You can test it http://www.szold.org.il/product/%d7%aa%d7%9b%d7%a0%d7%99%d7%95%d7%aa-%d7%94%d7%aa%d7%a2%d7%a8%d7%91%d7%95%d7%aa-%d7%94%d7%a2%d7%95%d7%a1%d7%a7%d7%95%d7%aa-%d7%91%d7%a7%d7%99%d7%93%d7%95%d7%9d-%d7%aa%d7%9c%d7%9e%d7%99%d7%93%d7%99/?attribute_pa_%25d7%259e%25d7%2595%25d7%2593%25d7%25a4%25d7%25a1=%25d7%25a2%25d7%2595%25d7%25aa%25d7%25a7-%25d7%259e%25d7%2595%25d7%2593%25d7%25a4%25d7%25a1-%25d7%2591%25d7%259e%25d7%25a9%25d7%259c%25d7%2595%25d7%2597-%25d7%2591%25d7%2593%25d7%2595%25d7%2590%25d7%25a8

And the problem only when user not login