#31 empty file when downloading inaccessible file

[Anonymous]

When users attempt to download a file they don't have access to, they may receive an empty, zero-length file or a blank page. This only occurs when a user follows a link that goes directly to the inaccessible file. If the user is simply browsing inaccessible files through the file manager, it is not issue because the download link is not available. We should detect inaccessible files before sending the file download headers. This will allow us to display an appropriate error message.