Probably the latter -- if it's present but empty (i.e., perfectly usable for a backup), it shouldn't complain about an empty dir. If it detects files, it can error (and possibly provide an option to clean or ignore the existing files in the directory before backing up).
Probably the latter -- if it's present but empty (i.e., perfectly usable for a backup), it shouldn't complain about an empty dir. If it detects files, it can error (and possibly provide an option to clean or ignore the existing files in the directory before backing up).