[CRASH] Turning sound on then off in-game reduces the FPS and then freezes/crashes the game

I was playing ARAM as Riot Kayle on Howling Abyss, on OS X El Capitan 10.11.6. I turned the sound on in-game only to be met by lowered FPS. I turned the sound back off, only for the game to freeze and crash. I didn't see a "bugsplat" window come up, just the new client and the Reconnect button.

1. Have in-game sound off before entering a game
2. Enter a game
3. Open in-game menu and turn on the sound
4. Have noticeably lower FPS
5. Open in-game menu and turn it back off
6. Freeze and crash