Trying to access array offset on null

#!/usr/bin/env php Testing ShipStation API Direct Connection ========================================== GA Warehouse Configuration: Trying to access array offset on null

ErrorException: Trying to access array offset on null in file /home/centralgoparts/public_html/test-scripts/test_shipstation_api_direct.php on line 23 #0 /home/centralgoparts/public_html/vendor/laravel/framework/src/Illuminate/Foundation/Bootstrap/HandleExceptions.php(255): Illuminate\Foundation\Bootstrap\HandleExceptions->handleError(2, 'Trying to acces...', '/home/centralgo...', 23) #1 /home/centralgoparts/public_html/test-scripts/test_shipstation_api_direct.php(23): Illuminate\Foundation\Bootstrap\HandleExceptions->{closure:Illuminate\Foundation\Bootstrap\HandleExceptions::forwardsTo():254}(2, 'Trying to acces...', '/home/centralgo...', 23) #2 {main}