Enable topic tracking for guests, as a guest search for unread topics:

[phpBB Debug] PHP Notice: in file /includes/functions.php on line 1403: Undefined variable: request

Fatal error: Call to a member function variable() on a non-object in /htdocs/pie/qi/boards/t3/includes/functions.php on line 1403

The line number is good with https://github.com/phpbb/phpbb3/pull/69.

There are multiple cases of missing $request globalization throughout includes/functions.php.

This also affects viewtopic, essentially rendering the board unusable for guests with guest topic tracking on.