Anivia 800 damage crit with no crit runes, masteries, or items!

I had finished playing an ARAM a few minutes ago and started looking through statistics, and I saw that I had the highest physical damage for our team. This wasn't that crazy, because we were an all AP team, but I thought it was a bit unusual because Anivia's auto animation is so slow and easy to cancel. So I checked critical strikes, only to find that I had an 800 damage crit, higher than the other team's Tryndamere with Static Shiv!

I was running no crit runes (I don't even own them), had no crit masteries, and bought no crit items. The game can be found here:

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1569630679/43145160?tab=stats

Strange!