--- Solr_Base_Query.php.bak	2009-12-21 18:14:36.000000000 +0100
+++ Solr_Base_Query.php	2009-12-21 18:16:59.000000000 +0100
@@ -322,7 +322,7 @@
         $queryvalues['filters'] .= ' ' . implode(' ', $values);
       }
     }
-    $queryvalues['filters'] = trim($queryvalues['filters']);
+    $queryvalues['filters'] = isset($queryvalues['filters']) ? trim($queryvalues['filters']) : '';
     $solrsort = $this->solrsort;
     if ($solrsort && ($solrsort['#name'] != 'score' || $solrsort['#direction'] != 'asc')) {
       if (isset($this->field_map[$solrsort['#name']])) {