Troubleshooting Mode: Use correct URL for the disable action in subdi…

…rectory scenarios.

When either WordPress is installed in a subdirectory, or a multisite is used, the path to the site is added to `site_url()`. The Troubleshooting Mode event of deactivating itself would append `$_SERVER['REQUEST_URI']` to this call, leading to unintentionally appending double subdirectory entries.

Props @ipajen.
Fixes #445.

mu-plugin/health-check-troubleshooting-mode.php

@@ -635,7 +635,13 @@ function disable_troubleshooting_mode() {
 	 */
 	private function get_clean_url( $url = null ) {
 		if ( ! $url ) {
-			$url = site_url( $_SERVER['REQUEST_URI'] );
+			// The full URL for the current request.
+			$raw_url = ( is_ssl() ? 'https://' : 'http://' ) . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
+
+			// We prepare the `REQUEST_URI` entry our selves, to account for WP installs in subdirectories or similar.
+			$request_uri = str_ireplace( site_url( '/' ), '', $raw_url );
+
+			$url = site_url( $request_uri );
 		}
 
 		return remove_query_arg( $this->available_query_args, $url );