Fix issue with building smart groups when is empty

[seamuslee001]

Overview

A brief description of the pull request. Keep technical jargon to a minimum. Hyperlink relevant discussions.

Before

Fixes an issue which was reported in stack exchange https://civicrm.stackexchange.com/questions/35868/smart-group-db-error and due to a $contctQueries array like

nothing... $contactQueries is
Array
(
    [0] => 
    [1] => SELECT 27 as group_id, contact_id as contact_id
       FROM   civicrm_group_contact
       WHERE  civicrm_group_contact.status = 'Added' AND civicrm_group_contact.group_id = 27 
)

After

Smart Groups build correctly

[civibot]

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