FIX #9663 merge data does not work in email templates

modules/templates/datasources/letterbox_attachment.php

@@ -96,7 +96,7 @@ if (!empty($res_id)) {
             $stmt = $dbDatasource->query('SELECT firstname, lastname, user_id, mail, phone, initials FROM users WHERE user_id = ?', [$res_contact_id]);
             $myContact = $stmt->fetch(PDO::FETCH_ASSOC);
             $datasources['contact'][] = $myContact;
-        } elseif (!empty($context)) {
+        } elseif (!empty($context) && !empty($datasources['res_letterbox'][0]['address_id']) && !empty($datasources['res_letterbox'][0]['contact_id'])) {
             $stmt = $dbDatasource->query('SELECT * FROM view_contacts WHERE contact_id = ? and ca_id = ?', array($datasources['res_letterbox'][0]['contact_id'], $datasources['res_letterbox'][0]['address_id']));
             $myContact = $stmt->fetch(PDO::FETCH_ASSOC);
             $myContact['postal_address'] = \Contact\controllers\ContactController::formatContactAddressAfnor($myContact);