Index: handlers/views_groupby_handler_field_groupfields.inc
===================================================================
--- handlers/views_groupby_handler_field_groupfields.inc	(revision 946)
+++ handlers/views_groupby_handler_field_groupfields.inc	(working copy)
@@ -70,12 +70,12 @@
     );
 
     $def_val2 = $this->options['views_groupby_fields_to_aggregate'];
-    $def_val2 = (empty($def_val2) || !is_array($def_val2)) ? array(t('-- None --')) : $def_val2;
+    $def_val2 = (empty($def_val2) || !is_array($def_val2)) ? array() : $def_val2;
 
     $form['views_groupby_fields_to_aggregate'] = array(
       '#title' => t('Fields to Aggregate with the SQL function'),
       '#type' => 'select',
-      '#options' => $options_fields,
+      '#options' => array(0 => t('-- None --')) + $options_fields,
       '#multiple' => TRUE,
       '#required' => TRUE,
       '#description' => t('Attention: in ANSI SQL you may not select fields that are used in grouping! If you do, Views will ignore them anyway'),
@@ -229,8 +229,7 @@
     $orderby_dir =  $this->options['views_groupby_sortby_direction'];
 
     // If group_by or to_aggregate lists are empty nothing should be done. 
-    if ((!is_array($to_group) || sizeof($to_group) < 1) ||
-        (!is_array($to_aggregate) || sizeof($to_aggregate) < 1)) {
+    if ((!is_array($to_group) || sizeof($to_group) < 1)) {
       return;
     }
 
@@ -261,7 +260,7 @@
     $views_fields = $this->_get_views_fields($just_aliases = TRUE);
 
     // Add all other fields into count, to ensure they do not mess up group_by.
-    if (is_array($this->query->fields)) {
+    if (is_array($this->query->fields) && is_array($to_aggregate)) {
       foreach ($this->query->fields as $key => $field) {
         if (in_array($key, $to_aggregate)) {
           if ($sql_func == 'count') {