[Client] Bug with Client and Mastery Page

I wasn't fast enough in choosing the right masteries in Champion Select, so it was still opened as the game started. This is what happened after the game.

I could not press the continue button anymore, nor could I close the mastery page.

I know there are some issues with the mastery page in the Champion Selection, but this one was quite annoying...

I hope that someday there is the day, where no more problems with that mastery page will appear :-)