Error setting Data Directory

[mwfantasygrounds]

I am having an error updating FGU; with App directory set to D:\FGU and Data directory set to D:\FGU_DATA, it gives me the attached error message. I think this is a bug since the data directory and the app directory are not children of each other

edit: I was able to fix it by choosing a path on the C drive, then manually typing the path I wanted for the Data.