Notice: Undefined index: path

First, you should turn off error reporting being printed to the screen in your production environment.

This error is because the path key isn’t set due to your site being in the root directory. You can modify his code with the following:

Old

if ( trim($_CPRegisteredURL,'/') == trim($request,'/') ) {
    return ($string{0} == '/' ? '/' : '') . trailingslashit($url['path']) . $_CPRegisteredURL;
  }

New

$path = isset( $url['path'] ) ? trailingslashit($url['path']) : '/';

  if ( trim($_CPRegisteredURL,'/') == trim($request,'/') ) {
    return ($string{0} == '/' ? '/' : '') . $path . $_CPRegisteredURL;
  }

Since he hasn’t updated the plugin in over 8 months you’re probably safe editing the code directly.

Thank you so much fictiveweb. I was getting exactly the same error and your fix worked perfectly!