Error on index.php (Undefined index: QUERY_STRING)

I setup the forum minibb ver 2 on IIS, but there are an error on index.php (i didn't touch this file):
PHP Notice: Undefined index: QUERY_STRING in c:\inetpub\wwwroot\minibb\index.php on line 14
Someone help me

Right before this line, try to insert this code:

if(!isset($_SERVER['QUERY_STRING'])) $_SERVER['QUERY_STRING']='';