Try this code:
$queries[] = $db->simple_select(
"users u LEFT JOIN ".TABLE_PREFIX."sessions s ON (u.uid=s.uid)",
"s.sid, s.ip, s.time, s.location, u.uid, u.username, u.invisible, u.usergroup, u.displaygroup",
"u.lastactive > $timesearch AND u.postnum > 0 ORDER BY u.username ASC, s.time DESC"
);
$queries[] = $db->simple_select(
"sessions s LEFT JOIN ".TABLE_PREFIX."users u ON (s.uid=u.uid)",
"s.sid, s.ip, s.uid, s.time, s.location, u.username, u.invisible, u.usergroup, u.displaygroup",
"s.time>'$timesearch' AND u.postnum > 0 ORDER BY u.username ASC, s.time DESC"
);
I just added an additional WHERE
clause that checks the postnum
field to make sure it's greater than 0.