Undefined index: order-received

Hello

I have just purchased the plugin and I am testing it, but there seems to be a huge issue on the confirmation page.

The order goes through just fine, but I get a huge amount of notices like this one:

Notice: Undefined index: order-received in /home/cerny/modernypraclovek.sk/wp-content/plugins/woocommerce-multi-currency/frontend/symbol.php on line 154

I am using 2 currencies (EUR and CZK)

This only affects the confirmation page
Please let me know ho to fix this.