Minecraft crashes on menu screen (pre-release 9)

Loading up pre release 9, the minecraft launcher crashes. The window stops responding, and CPU hits 100% as soon as it hits the last line in the launcher log (error).

Checking Launcher logs, the last lines to be reported each time I've tried is:

[0716/172402:INFO:GameCallbacks.cpp(193)] game/net.minecraft.realms.RealmsBridge (Client thread) error Realms module missing

 

Attaching launcher log, which only has two attempts in it (I renamed the old log so we could get only relevant data). Happy to produce more attempts.