fix to whereIn to prevent invalid SQL being generated when no params are passed

lib/Doctrine/Query/Abstract.php

@@ -1136,6 +1136,11 @@ abstract class Doctrine_Query_Abstract
     public function whereIn($expr, $params = array(), $not = false)
     {
         $params = (array) $params;
+
+        // if there's no params, return (else we'll get a WHERE IN (), invalid SQL)
+        if (!count($params))
+          return;
+
         $a = array();
         foreach ($params as $k => $value) {
             if ($value instanceof Doctrine_Expression) {