Attaching a file to a release node results in wrong filepath stored in DB

In testing http://drupal.org/node/185244 I noticed a rather serious bug in how project_release handles file attachments when cvslog.module is disabled. Not sure when this was broken, but at least on my test site, if you try to manually attach a file to a release node (not via upload.module, but the hard-coded file attachment stuff), it saves the record in the {project_release_nodes} table using the tmp filepath, not the real one. Something about how the preview workflow is happening is screwing things up.

A little debugging shows that by the time we hit project_release_db_save() on the initial submit of the release node, $node->file_path is already set to, for example "/tmp/foo.txt". At that point, $file_data->filepath is correctly set to "files/foo.txt".

So, the bug is in this bit of logic:

 'file_path' => $node->file_path ? $node->file_path : $file_data->filepath,

That's the wrong way to go about it. Instead of seeing if $node already has a value, we should just see if we got a new file_path from $file_data, and if not, fall back to what's already in $node.

Attached patch works fine with my local testing, but I wouldn't mind more tests and an independent review. ;)