Youtube virus warning?!

Hello Avast-team, I just registered on this site because I got a really confusing virus warning just a few minutes ago. I was just in the middle of watching some Youtube videos, when all of a sudden this virus warning popped up: http://imgur.com/lqsehAi - can anyone tell me why? I can’t really imagine Google actually spreading viruses, is this some kind of false alarm thing or something else? Don’t really know what to think of it, but I’m a bit worried…

See: https://forum.avast.com/index.php?topic=199217.0