woothemes/woocommerce — comment on commit 3d18b7d698f1d4b04e588ffd4f680441c9249611
File:  line 0
By GeertDD:

I'm on Apache 2.2 (localhost), but I found out what is going on. `wp_get_referer()` returns false if the referer is the same as te current request URL. This is the case since you are being redirected back to the cart page. This should fix it

`$referer = ( wp_get_referer() ) ? wp_get_referer() : $woocommerce->cart->get_cart_url();
wp_safe_redirect ( $referer );
exit;`