Slim Application Error

The application could not run because of the following error:

Details

Type: ErrorException
Code: 8
Message: Undefined index: product
File: /home/multibiz/web/lukisankaligrafi.com/public_html/controller/Main.php
Line: 136

Trace

#0 /home/multibiz/web/lukisankaligrafi.com/public_html/controller/Main.php(136): Slim\Slim::handleErrors(8, 'Undefined index...', '/home/multibiz/...', 136, Array)
#1 [internal function]: controller\Main->categoryAction('asmaul-husna')
#2 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slimcontroller/slimcontroller/src/SlimController/Slim.php(176): call_user_func_array(Array, Array)
#3 [internal function]: SlimController\Slim->SlimController\{closure}('asmaul-husna')
#4 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slim/slim/Slim/Route.php(468): call_user_func_array(Object(Closure), Array)
#5 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slim/slim/Slim/Slim.php(1357): Slim\Route->dispatch()
#6 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slim/slim/Slim/Middleware/Flash.php(85): Slim\Slim->call()
#7 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slim/slim/Slim/Middleware/MethodOverride.php(92): Slim\Middleware\Flash->call()
#8 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slim/slim/Slim/Middleware/PrettyExceptions.php(67): Slim\Middleware\MethodOverride->call()
#9 /home/multibiz/web/lukisankaligrafi.com/public_html/vendor/slim/slim/Slim/Slim.php(1302): Slim\Middleware\PrettyExceptions->call()
#10 /home/multibiz/web/lukisankaligrafi.com/public_html/index.php(39): Slim\Slim->run()
#11 {main}