A couple of issues that this causes:

• Clicking on "Browse" for game directory does nothing
• Setting the game directory path to "/home/username/.minecraft/profilename" crashes the game

EDIT: I wrote some things about how I faked a windows file format to sort it out. Turns out that only works once.

This issue is well beyond me and this bug report may be useless.

(Apologies for the bad bug report format; I am not good with these.)