"Unexpected Platform Error" on Masteries Pages
I'm running the Mac client and since the 5.22 patch this morning I'm unable to edit or create new mastery pages. Every time I try I get the client error "Unexpected Platform Error". The changes I make to the mastery pages seem to save, but when I try to use them in game it shows I have no masteries, and when I go back to my masteries page after the game, it shows the page I edited earlier as blank.
This is incredibly frustrating and means I can't compete in lane at all. Essentially making the game unplayable until it's fixed.
If someone could please help me out with this I would be highly appreciative.