Why do I encounter a check out problem when deleting an item?

[sahar5]

Hello,

when i have tree or more items in my basket and I want to delete one item i get this error. See the Screenshot. I have dawn Theme.

then I have to click "go to previous page" so it goes back to my basket. The item is deleted but I don't want to get this error. 

Website: www.sahar-fashion.com