private function _end_null()
 {
     $null = $this->_buffer;
     if ($null === 'null') {
         $this->_listener->value(null);
     } else {
         throw new JsonStreamingParser_ParsingError($this->_line_number, $this->_char_number, "Expected 'null'. Got: " . $null);
     }
     $this->_buffer = '';
     $this->_state = self::STATE_AFTER_VALUE;
 }