Validation of NDIR Source or NCD

Better error reporting if possible instead of SIO Error, NCD seems to accept anything without validation destination exist, NDIR of the non existing directory simply generates SIO Error Thanks

Locate the command-handling entry points for NCD and NDIR, then reproduce the behavior with a missing destination and an invalid or nonexistent source directory. Determine how the current SIO Error is produced; done means invalid paths are validated and report a more specific error, with the behavior covered by the relevant tests if they exist.

Written by the indexing model from the issue text.