Ignore non-numeric page args

Passing these causes notices, and is an error on newer PHP versions.

application/libraries/Omeka/Db/Table.php

@@ -404,7 +404,7 @@ public function applySorting($select, $sortField, $sortDir)
      */
     public function applyPagination($select, $limit, $page = null)
     {
-        if ($page) {
+        if ($page && is_numeric($page)) {
             $select->limitPage($page, $limit);
         } else {
             $select->limit($limit);