This happens whenever I try to change my directory in the new beta

Whenever I try changing game directories I get this random error, I don't know if this is a bug or an upcomming feature but I dont like. Pls fix so I can have multiple directories. And now for some feedback: PLEASE MAKE IT EASIER TO SWITCH BETWEEN BETA AND NORMAL LAUNCHER CUS NOW I HAVE TO REINSTALL LAUNCHER (sorry for caps).