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Fatal error: Uncaught TypeError: substr(): Argument #1 ($string) must be of type string, null given in /opt/dbis-projekt/dbis_server/src/Action/Frontend/Admin/AdminBasePage.php:91 Stack trace: #0 /opt/dbis-projekt/dbis_server/src/Action/Frontend/Admin/AdminBasePage.php(91): substr() #1 /opt/dbis-projekt/dbis_server/vendor/php-di/php-di/src/Definition/Resolver/ObjectCreator.php(143): App\Action\Frontend\Admin\AdminBasePage->__construct() #2 /opt/dbis-projekt/dbis_server/vendor/php-di/php-di/src/Definition/Resolver/ObjectCreator.php(71): DI\Definition\Resolver\ObjectCreator->createInstance() #3 /opt/dbis-projekt/dbis_server/vendor/php-di/php-di/src/Definition/Resolver/ResolverDispatcher.php(71): DI\Definition\Resolver\ObjectCreator->resolve() #4 /opt/dbis-projekt/dbis_server/vendor/php-di/php-di/src/Container.php(390): DI\Definition\Resolver\ResolverDispatcher->resolve() #5 /opt/dbis-projekt/dbis_server/vendor/php-di/php-di/src/Container.php(139): DI\Container->resolveDefinition() #6 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/CallableResolver.php(129): DI\Container->get() #7 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/CallableResolver.php(90): Slim\CallableResolver->resolveSlimNotation() #8 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/CallableResolver.php(63): Slim\CallableResolver->resolveByPredicate() #9 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/Routing/Route.php(340): Slim\CallableResolver->resolveRoute() #10 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(65): Slim\Routing\Route->handle() #11 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(65): Slim\MiddlewareDispatcher->handle() #12 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/Routing/Route.php(315): Slim\MiddlewareDispatcher->handle() #13 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/Routing/RouteRunner.php(68): Slim\Routing\Route->run() #14 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/Middleware/BodyParsingMiddleware.php(64): Slim\Routing\RouteRunner->handle() #15 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(121): Slim\Middleware\BodyParsingMiddleware->process() #16 /opt/dbis-projekt/dbis_server/vendor/slim/twig-view/src/TwigMiddleware.php(115): Psr\Http\Server\RequestHandlerInterface@anonymous->handle() #17 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(121): Slim\Views\TwigMiddleware->process() #18 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/Middleware/RoutingMiddleware.php(45): Psr\Http\Server\RequestHandlerInterface@anonymous->handle() #19 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(121): Slim\Middleware\RoutingMiddleware->process() #20 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/Middleware/MethodOverrideMiddleware.php(41): Psr\Http\Server\RequestHandlerInterface@anonymous->handle() #21 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(121): Slim\Middleware\MethodOverrideMiddleware->process() #22 /opt/dbis-projekt/dbis_server/vendor/selective/basepath/src/BasePathMiddleware.php(52): Psr\Http\Server\RequestHandlerInterface@anonymous->handle() #23 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(121): Selective\BasePath\BasePathMiddleware->process() #24 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/MiddlewareDispatcher.php(65): Psr\Http\Server\RequestHandlerInterface@anonymous->handle() #25 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/App.php(199): Slim\MiddlewareDispatcher->handle() #26 /opt/dbis-projekt/dbis_server/vendor/slim/slim/Slim/App.php(183): Slim\App->handle() #27 /opt/dbis-projekt/dbis_server/public/index.php(45): Slim\App->run() #28 {main} thrown in /opt/dbis-projekt/dbis_server/src/Action/Frontend/Admin/AdminBasePage.php on line 91