[CLIENT] Negative IP after buying a champion

I had just enough IP to buy Shyvana (I believe I had 3176), so I went to the store, clicked on the portrait, clicked Unlock Champion, unlocked with IP. As you can see, my IP counter went negative instead of subtracting. After restarting the client, I had the correct amount displayed. I have not been able to reproduce the issue (I don't have any more IP.)