[Client] "Unexpected Platform Error"

So I was in champ select and I created a new mastery page and it said "Unexpected Platform Error", I didn't think much about it. I continue setting up my mastery page and get into game and it selected the mastery page I had from the previous game, which was not what I wanted.

It appears to actually be the entire masteries themselves. Anything I do with them results in said error pop up.