- fix for skip_deleted (#1485553)

program/include/rcube_imap.php

@@ -982,10 +982,14 @@ class rcube_imap
    * @access private
    * @see rcube_imap::search()
    */
-  function _search_index($mailbox, $criteria='ALL', $charset='', $sort_field='')
+  function _search_index($mailbox, $criteria='ALL', $charset=NULL, $sort_field=NULL)
     {
     if ($this->get_capability('sort'))
+      {
+      $sort_field = $sort_field ? $sort_field : $this->sort_field;
+      $charset = $charset ? $charset : $this->default_charset;
       $a_messages = iil_C_Sort($this->conn, $mailbox, $sort_field, $criteria, FALSE, $charset);
+      }
     else
       $a_messages = iil_C_Search($this->conn, $mailbox, ($charset ? "CHARSET $charset " : '') . $criteria);