Unknown error is sending to slack channel from lumen application

To get notify for uncatched and internal errors, I made the following changes to render function in Handler.php

if (App::environment('production')) { Log::channel('slack')->err($ex->getMessage() . '-' . $ex->getTraceAsString()); }

After this, I'm seeing the following errors are triggered to my slack channel but I'm not getting the reason for this error

(Array) #1 /var/www/html/my-application/vendor/laravel/lumen-framework/src/Concerns/RoutesRequests.php(418): Laravel\Lumen\Application->Laravel\Lumen\Concerns\{closure}(Object(Laravel\Lumen\Http\Request)) #2 /var/www/html/my-application/vendor/laravel/lumen-framework/src/Concerns/RoutesRequests.php(171): Laravel\Lumen\Application->sendThroughPipeline(Array, Object(Closure)) #3 /var/www/html/my-application/vendor/laravel/lumen-framework/src/Concerns/RoutesRequests.php(108): Laravel\Lumen\Application->dispatch(NULL) #4 /var/www/html/my-application/public/index.php(28): Laravel\Lumen\Application->run() #5 {main}

Anyhow of you have an idea on this error?