Originally Posted by Lori:
Well, I can't get the error to happen no matter what I do... 
But I'll take your word for it. 
If you want to get an error just select a non-graphics file such as a word document though you have to choose all files from the file selector.
I've also just made a false graphics file by changing the suffix on a word document file to jpg to make it look as if it's a graphics file. Not surprsingly that produced an error with the popup message Bad Request but as before no link.