41.16 Non-striker leaving his/her ground early
If the non-striker is out of his/her ground from the moment the ball comes into play to the instant when the bowler would normally have been expected to release the ball, the bowler is permitted to attempt to run him/her out. Whether the attempt is successful or not, the ball shall not count as one in the over.
At first look to me I thought Buttler was in at the time you would have expected Ashwin to release the ball.