Slim Application Error

The application could not run because of the following error:

Details

Type: UnexpectedValueException
Message: Middleware must return instance of \Psr\Http\Message\ResponseInterface
File: /chroot/home/spectora/spectorandco.com/html/spector/vendor/slim/slim/Slim/MiddlewareAwareTrait.php
Line: 72

Trace

#0 /chroot/home/spectora/spectorandco.com/html/spector/vendor/akrabat/rka-slim-session-middleware/RKA/SessionMiddleware.php(47): Slim\App->Slim\{closure}(Object(Slim\Http\Request), Object(Slim\Http\Response))
#1 [internal function]: RKA\SessionMiddleware->__invoke(Object(Slim\Http\Request), Object(Slim\Http\Response), Object(Closure))
#2 /chroot/home/spectora/spectorandco.com/html/spector/vendor/slim/slim/Slim/DeferredCallable.php(43): call_user_func_array(Object(RKA\SessionMiddleware), Array)
#3 [internal function]: Slim\DeferredCallable->__invoke(Object(Slim\Http\Request), Object(Slim\Http\Response), Object(Closure))
#4 /chroot/home/spectora/spectorandco.com/html/spector/vendor/slim/slim/Slim/MiddlewareAwareTrait.php(70): call_user_func(Object(Slim\DeferredCallable), Object(Slim\Http\Request), Object(Slim\Http\Response), Object(Closure))
#5 /chroot/home/spectora/spectorandco.com/html/spector/vendor/slim/slim/Slim/MiddlewareAwareTrait.php(117): Slim\App->Slim\{closure}(Object(Slim\Http\Request), Object(Slim\Http\Response))
#6 /chroot/home/spectora/spectorandco.com/html/spector/vendor/slim/slim/Slim/App.php(406): Slim\App->callMiddlewareStack(Object(Slim\Http\Request), Object(Slim\Http\Response))
#7 /chroot/home/spectora/spectorandco.com/html/spector/vendor/slim/slim/Slim/App.php(314): Slim\App->process(Object(Slim\Http\Request), Object(Slim\Http\Response))
#8 /chroot/home/spectora/spectorandco.com/html/spector/public/index.php(11): Slim\App->run()
#9 {main}