Error with function_login.php

[jasonpeinko]

i get this error

Fatal error: call to a member function on a non-object in /home/pinkofer/public_html/forums/includes/functions_logn.php on line 130

this is the function that includes like 130

function exec_unstrike_user($username)
{
	global $vbulletin;

	$vbulletin->db->query_write("DELETE FROM " . TABLE_PREFIX . "strikes WHERE strikeip = '" . $vbulletin->db->escape_string(IPADDRESS) . "' AND username='" . $vbulletin->db->escape_string(htmlspecialchars_uni($username)) . "'");
}

I get this error when using drupaltin product.