CSV export bogus redirect if no rows to export

[cheesegrits]

See:

http://fabrikar.com/forums/showthread.php?p=149721#post149721

if we think there are no rows to export, we're doing a 303 redirect, which blows up the AJAX calling code.

To replicate, try doing a CSV export (front or back end) on an empty List, and look at the Console tab in Firebug.

-- hugh