Hopefully you’ve fixed this by now, but for anyone else having this problem, i have found the solution.

In wp-admin\includes\screen.php on line 706:

<?php echo self::$this->_help_sidebar; ?>

needs to have self:: removed, so it becomes:

<?php echo $this->_help_sidebar; ?>

That will fix your problem.

Upvote the original solver on stackoverflow if you like.