Redirect user back to the current page instead of Homepage

There's a browser redirection that happens on occasion where when a user visits a Drupal page, they get redirected to the homepage. This happens in a few places, but the most common is when the user has cookies saved, and they open a web browser and directly type in a Drupal page. When that first page loads, _phpbbforum_authenticate_user() is called which then calls _phpbbforum_login_external() without a URL and that redirects the user to the homepage. So I've created a patch to redirect the user back to the page they were trying to reach instead of being redirected to the homepage.

Please confirm that this is the best way to fix this issue. Also, my site is displaying phpBB "In the window", so I don't know how this would affect sites that are displayed the other two ways.