The bottom of the mastery page section of the collection has a large blank area.
It actually looks like there is supposed to be something down there, based on how crowded the rest of the client window currently is.
Moving the whole trees down, or spreading it out some to increase the room between tiers slightly would fill that space in better.
This board is the best place to discuss the client with Rioters and your fellow players, although it won't be our main source for feedback resolution. Look to the other tools, like the Submit Feedback button in the client, for that. As always, please follow the Universal Rules and keep content focused on appropriate topics for this board.