Affected version: 2.0.757 (Windows)
The bug
The launcher erases the profile directory if it does not exist. The expected behavior is that it leaves the set directory untouched and shows an error when you try to start Minecraft.
Note: The launcher accepts valid file paths however even though it cannot launch because it requires a folder path.
How to reproduce
Start creating a new profile
Enter an invalid profile directory
Save the profile and open the editing window
→ You will see that the profile directory is empty
Seems to be "fixed" in 2.0.934; the launcher now converts invalid inputs like
asf#asf,clVMDS;DAS#ä+#
toC:/Users\<user>\AppData\Roaming\.minecraft\asf#asf,clVMDS;DAS#ä+#
.