Deleting files on an external FTP server via the FTP client creates an exception

[PumpkinMH]

Whenever I added an FTP server to the app, i could browse files just fine and even create files, but whenever I try to delete a file, it doesn't work, and instead created a toast indicating an exception. Using other android ftp clients allows me to delete the file just fine, but Material Files can't do it for some reason

[zhanghai]

What is that exception?