Slim Application Error

The application could not run because of the following error:

Details

Type: ErrorException
Code: 2
Message: Undefined variable $user_id
File: /usr/www/users/rindei/docroot/rinderallianz.de/daten/index.php
Line: 54

Trace

#0 /usr/www/users/rindei/docroot/rinderallianz.de/daten/index.php(54): Slim\Slim::handleErrors()
#1 [internal function]: {closure}()
#2 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Slim.php(1210): call_user_func_array()
#3 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Slim.php(1356): Slim\Slim->applyHook()
#4 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Middleware/Flash.php(85): Slim\Slim->call()
#5 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Middleware/MethodOverride.php(92): Slim\Middleware\Flash->call()
#6 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Middleware/SessionCookie.php(110): Slim\Middleware\MethodOverride->call()
#7 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Middleware/PrettyExceptions.php(67): Slim\Middleware\SessionCookie->call()
#8 /usr/www/users/rindei/docroot/rinderallianz.de/daten/vendor/slim/slim/Slim/Slim.php(1302): Slim\Middleware\PrettyExceptions->call()
#9 /usr/www/users/rindei/docroot/rinderallianz.de/daten/index.php(658): Slim\Slim->run()
#10 {main}