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When Uploading an empty file through the REST API (POST to /uploads.json), the response is 201 Created, and an invalid token (which that does not resolve to an attachment through Attachment.find_by_token because it lacks the digest component) is returned. However an attachment record is still saved, but without a corresponding file in the file system.

When looking into this I found that the easiest fix for this would be to change the two conditionals in attachment.rb that prevent an empty file from being treated like any non-empty file. I don't see any technical reason to not allow the uploading of empty files, and my change doesn't seem to cause any of the existing tests to fail.

Attached is a patch which does that, including a test case illustrating the inconsistent API behavior I described above.