Making sure empty $values parameter is sent as array() (Bug #1400514)

To test: checkout master - try and add a comment to a page on page
reload you should get an error

With patch - adding/viewing comments should work again

Change-Id: Ic32a5f7daf273385b745c57622abac369e388197
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>

htdocs/artefact/lib.php

@@ -1117,7 +1117,7 @@ abstract class ArtefactType implements IArtefactType {
             FROM {artefact_attachment} aa
                 INNER JOIN {artefact} a ON aa.attachment = a.id
                 LEFT JOIN {artefact_file_files} f ON a.id = f.artefact
-            WHERE aa.artefact IN (' . join(', ', array_map('intval', $artefactids)) . ')', '');
+            WHERE aa.artefact IN (' . join(', ', array_map('intval', $artefactids)) . ')', array());
         if (!$attachments) {
             return array();
         }