Tweaks to a couple queries for post counts to make for postgres friendly 2, a=chris

diff --git a/src/models/GroupModel.php b/src/models/GroupModel.php
index f049784f0..1985bb2e6 100644
--- a/src/models/GroupModel.php
+++ b/src/models/GroupModel.php
@@ -1320,7 +1320,6 @@ class GroupModel extends Model implements MediaConstants
     public function getUserPostCount($user_id, $timestamp = 0)
     {
         $db = $this->db;
-        $personal_group_id = $this->getPersonalGroupId($user_id);
         $subselect = "(SELECT GROUP_ID " .
             "FROM USER_GROUP WHERE USER_ID = ? AND STATUS = ".
             C\ACTIVE_STATUS . ")";