Blank uuid supplied for file download results in problems.

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Edit a species profile page.
2. Add a profile element of type image.
3. Don't supply a filename.

What is the expected output? What do you see instead?
A couple of things
1) ideally blank images would be disallowed.
2) The file download controller redirects the user to a URL of the form 
<server>/<bdrs context path>/

On the Atlas BDRS install at least, this results in the user being logged out 
of the current portal in the background which is confusing.

Please use labels and text to provide additional information.

Original issue reported on code.google.com by chris.go...@gmail.com on 9 Jan 2013 at 3:46

[GoogleCodeExporter]

This is related to Issue 353

Original comment by chris.go...@gmail.com on 9 Jan 2013 at 4:18

[GoogleCodeExporter]

I propose two changes.
1) Change the DownloadFileController to treat a blank uuid the same as an 
absent one (and send a 404)
2) Change the redirect to include the portal context path.

Original comment by chris.go...@gmail.com on 9 Jan 2013 at 4:19

[GoogleCodeExporter]

I'm unwilling at this stage to fix the page validation as this is one of the 
pages affected by ketchup performance.  Adding dynamic revalidation of the 
ketchup fields would kill the page completely.

Original comment by chris.go...@gmail.com on 9 Jan 2013 at 4:20