weird error message, if the output directory doesn't exist

[eps696]

hi, thanks for this cool tool. when runnning windows executable against existing input directory (but without existing output one), it fails with the message: invalid outputpath extension type. it's not a big deal to create output directory beforehand manually, but it really took a while to understand first time what was the actual problem. it would be very helpful either to change that message to something more meaningful, or (better) to add output directory auto-creation.