[Gameplay] Erroneous Screen Flashing and Graphics

In playing League of Legends, pretty consistently almost every game I'll get a random screen flash, even though I have flashing turned off for damage and such, and even though nothing is currently happening. I happen to stream now and then and caught a game where I had this weird swirl appear, and when I froze the frame, I saw exactly what this particular bug was, a giant mini map icon of Vlad! Does the screen flash or do weird graphic glitches like this to anyone else? What in the world is this from? I attached a pic of what I'm talking about.

At the time I was waiting for minions to spawn down my lane, playing Miss Fortune and standing in the river close to Blue Buff literally doing nothing.