Handle filter[query] not being defined

web/includes/functions.php

@@ -1157,7 +1157,7 @@ function sortHeader($field, $querySep='&') {
   global $view;
   return implode($querySep, array(
     '?view='.$view,
-    'page=1'.(isset($_REQUEST['filter'])?$_REQUEST['filter']['query']:''),
+    'page=1'.((isset($_REQUEST['filter']) and isset($_REQUEST['filter']['query'])) ? $_REQUEST['filter']['query'] : ''),
     'sort_field='.$field,
     'sort_asc='.( ( isset($_REQUEST['sort_field']) and ( $_REQUEST['sort_field'] == $field ) ) ? !$_REQUEST['sort_asc'] : 0),
     'limit='.(isset($_REQUEST['limit']) ? validInt($_REQUEST['limit']) : ''),