Bug in debug.php

Current version line 269 has this:

$x_via ? ? = ( is_numeric( strpos( $headers['Via'], 'arnish' ) ) ) ? true : false;

The problem is that $headers['Via'] can be an *array* of headers which causes a fatal error in newer versions of PHP.

To reproduce, ensure, there are more than one Via header, go to the “Check caching” page and purge.