Magento

Hi all,

We are using pay u payment gateway for our site
After redirecting to payment site if we do not enter any detail and press browsers back button then magento gives error
“Fatal error: Call to a member function getMethodInstance() on a non-object in /home/content/70/10318970/html/beta/app/code/core/Mage/Payment/Model/Observer.php on line 45”

and shopping cart is not empty but order is placed with status as ‘processing’.

One more issue:
If we select COD as payment option then it places order but shopping cart is not empty

Thanks,
sneha