$session['sessionurl'] no value in showthread.php - why?

[Spinball]

Thanks MarcoH64,
this is a slight modification to showthread.php just before the

PHP Code:

// #############################################################################
// output page 


bit at the bottom. I would have thought that the session variable would already be populated since it's being used elsewhere in the script.
I tried [sessionhash] aswell but that was empty, too.