Blank screen after minions spawn

So I just join a game, and as I was setting up my tentacles in my lane ( is illioa) when all of a sudden my screen went blank, I can hear the game, but I couldn't see jack. When I tried tabbing out, it wouldn't let me, task manager isn't popping up either 'cause the black screen, that is my client, won't move. And yes I know, I can just restart my computer, but I didn't save my resume, so I'm kinda stuck, and I'm wondering, is there a way to close the game without task manager