Found a problem with unlink

Hi,

I've downloaded this package and using it - it is very great.
However, I've encountered a problem and had to change the source code of archive.php, as it adds the base dir to the file path for unlink.
This fails since when the tmp file is not under the base dir
(when the archive file is created with a full path).
Better add a check if file exists before unlinking it,
in order to avoid warning message in the log.

Ilan.