Its to stop abuse, if you end a fight that did not exist or did not actually end it will take you to that page. Do not go to the page directly.
You will be directed there at the end of an attack and it will show the correct information. You cannot refresh that page. Granted it should show a "You cannot refresh this page" message and possibly direct you to the information of your last attack (say if torn disconnects whilst it is loading).
You more than likely double clicked either 'Leave', 'Mug' or 'Hospitalize'.. I have done it before on accident and had the error too.
You still win the attack, and money if mugged, exp if left and so on!