Error

ERROR: mb_strlen(): Argument #2 ($encoding) must be a valid encoding, "255" given {"exception":"[object] (ValueError(code: 0): mb_strlen(): Argument #2 ($encoding) must be a valid encoding, \"255\" given at /var/www/vendor/laravel/framework/src/Illuminate/Support/Str.php:477)
[stacktrace]
#0 /var/www/vendor/laravel/framework/src/Illuminate/Support/Str.php(477): mb_strlen('', '255')
#1 /var/www/vendor/laravel/framework/src/Illuminate/Support/Stringable.php(371): Illuminate\\Support\\Str::length('', 255)
#2 /var/www/app/Providers/AppServiceProvider.php(133): Illuminate\\Support\\Stringable->length(255)
#3 /var/www/vendor/guzzlehttp/promises/src/FulfilledPromise.php(41): Illuminate\\Http\\Client\\Factory->App\\Providers\\{closure}(Object(GuzzleHttp\\Psr7\\Response))
#4 /var/www/vendor/guzzlehttp/promises/src/TaskQueue.php(48): GuzzleHttp\\Promise\\FulfilledPromise::GuzzleHttp\\Promise\\{closure}()
#5 /var/www/vendor/guzzlehttp/promises/src/Promise.php(248): GuzzleHttp\\Promise\\TaskQueue->run(true)
#6 /var/www/vendor/guzzlehttp/promises/src/Promise.php(224): GuzzleHttp\\Promise\\Promise->invokeWaitFn()
#7 /var/www/vendor/guzzlehttp/promises/src/Promise.php(269): GuzzleHttp\\Promise\\Promise->waitIfPending()
#8 /var/www/vendor/guzzlehttp/promises/src/Promise.php(226): GuzzleHttp\\Promise\\Promise->invokeWaitList()
#9 /var/www/vendor/guzzlehttp/promises/src/Promise.php(62): GuzzleHttp\\Promise\\Promise->waitIfPending()
#10 /var/www/vendor/guzzlehttp/guzzle/src/Client.php(187): GuzzleHttp\\Promise\\Promise->wait()
#11 /var/www/vendor/laravel/framework/src/Illuminate/Http/Client/PendingRequest.php(962): GuzzleHttp\\Client->request('POST', 'http://pacific-...', Array)
#12 /var/www/vendor/laravel/framework/src/Illuminate/Http/Client/PendingRequest.php(823): Illuminate\\Http\\Client\\PendingRequest->sendRequest('POST', 'http://pacific-...', Array)