view.LFTPD: handle app logic errors from `App.backend.req()`
view.LFTPD: handle app logic errors from `App.backend.req()`

Signed-off-by: Oleg Verych <a5ce24b76737c0ca6b8faa55c4f938064a1695cf@gmail.com>

suprojs/suprolftpd,suprojs/suprolftpd