It's this line:
Code:#
#-----[ FIND ]------------------------------------------
#
$user_sig = ( $postrow[$i]['enable_sig'] && $postrow[$i]['user_sig'] != '' && $board_config['allow_sig'] ) ? $postrow[$i]['user_sig'] : '';
#
#-----[ REPLACE WITH ]------------------------------------
#
$user_sig = ( $postrow[$i]['enable_sig'] && $postrow[$i]['user_sig'] != '' && $board_config['allow_sig'] && $userdata['session_logged_in'] ) ? $postrow[$i]['user_sig'] : '';