[CLIENT] Pressing Space ~3 times while in masteries causes a client-wide UI issue

While doing masteries, pressing space 3 or so times causes the UI to get blocked by a big white space (see screenshot). This caused me to get dropped from a ranked match, lose LP, and have a wait timer. It covers most of the ui (on any page) until the user relogs LoL.

1. Go to masteries
2. Press space 3 times
3. Observe user cannot use UI blocked by white space
4. ggwp have to relog.

This has been seen by many players across the LoL community.