Last modified: 2010-05-15 15:48:21 UTC
redirect.php uses and needs $wgArticlePath which in a default install is only
set in Setup.php. Setup.php gets loaded from WebStart.php only if MW_NO_SETUP
isn't set, but redirect.php sets it, and thus prevents loading of Setup.php and
any value for $wgArticlePath.
All of this thus causes redirect.php to outpur an empty Location-header.
Fixed a long time ago in r23243.