After login, redirect to the original URL called

Fix an annoying issue in Admin, when loading an inner page
(`/admin/pages/whatever`) and I'm logged out, after login I'm always
sent to the dashboard, while it should bring to the page I called in
the first place

classes/admin.php

@@ -185,8 +185,7 @@ class Admin
                     $grav = $this->grav;
 
                     $this->setMessage($this->translate('PLUGIN_ADMIN.LOGIN_LOGGED_IN'), 'info');
-                    $redirect_route = $this->uri->route();
-                    $grav->redirect($redirect_route);
+                    $grav->redirect($form['redirect']);
                 }
             }
         }