When accessing the backoffice using URL with "app.php" (for example http://ezplatform.dev/app.php/ez) it is not possible to log in. The user is immediately redirected to login page and there is an error showing in the console: "_ezcombo?app-base/app-base-min.js&querystring-stringify-simple/querystring-stringify-simple-min.js&…:1687 POST http://ezplatform.dev/app.php/app.php/api/ezp/v2/user/sessions/r04atonm3r2i8n7l630r8o66ik/refresh 404 (Not Found)". Also, when you click the "Login" button, the login page displays an error "An unexpected error occurred" and there is an error in the console: "_ezcombo?app-base/app-base-min.js&querystring-stringify-simple/querystring-stringify-simple-min.js&…:1687 POST http://ezplatform.dev/app.php/app.php/api/ezp/v2/user/sessions 404 (Not Found)".
The URLs of these requests have the "app.php" two times, which means it is duplicated. Removing the duplication should resolve the bug.

Steps to reproduce

1. Create fresh eZ Platform installation under a domain, for example http://ezplatform.dev.
2. Try to access backoffice through this URL: http://ezplatform.dev/app.php/ez.
3. Confirm that it caused 404 error in the console and redirection to the login page.
4. Click "Login" button.
5. Confirm that it caused another 404 error in the console and "An unexpected error occurred" is displayed.