function cleanup_shortcode_fix($content) {
          $array = array (
            '<p>[' => '[',
            ']</p>' => ']',
            ']<br />' => ']',
            ']<br>' => ']'
          );
          $content = strtr($content, $array);
            return $content;
        }
        add_filter('the_content', 'cleanup_shortcode_fix');

$string=preg_replace_('/<p>s*</p>/', '', $string);

add_filter('the_content', 'cleanup_shortcode_fix', 1);