帮忙看看这个是什么错误

ErrorException: Undefined index: created_at

in /www/wwwroot/www.jmt.cn/module/WenkuTopic/Api/Controller/WenkuTopicController.php:62

Stack trace:

#0 /www/wwwroot/www.jmt.cn/module/WenkuTopic/Api/Controller/WenkuTopicController.php(62): Illuminate\Foundation\Bootstrap\HandleExceptions->handleError(8, 'Undefined index...', '/www/wwwroot/ww...', 62, Array)

#1 /www/wwwroot/www.jmt.cn/module/WenkuTopic/Web/Controller/WenkuTopicController.php(7): Module\WenkuTopic\Api\Controller\WenkuTopicController->get()

#2 [internal function]: Module\WenkuTopic\Web\Controller\WenkuTopicController->show('34')

#3 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Controller.php(256): call_user_func_array(Array, Array)

#4 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(164): Illuminate\Routing\Controller->callAction('show', Array)

#5 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(112): Illuminate\Routing\ControllerDispatcher->call(Object(Module\WenkuTopic\Web\Controller\WenkuTopicController), Object(Illuminate\Routing\Route), 'show')

#6 [internal function]: Illuminate\Routing\ControllerDispatcher->Illuminate\Routing\{closure}(Object(Illuminate\Http\Request))

#7 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(139): call_user_func(Object(Closure), Object(Illuminate\Http\Request))

#8 [internal function]: Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#9 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(102): call_user_func(Object(Closure), Object(Illuminate\Http\Request))

#10 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(114): Illuminate\Pipeline\Pipeline->then(Object(Closure))

#11 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(68): Illuminate\Routing\ControllerDispatcher->callWithinStack(Object(Module\WenkuTopic\Web\Controller\WenkuTopicController), Object(Illuminate\Routing\Route), Object(Illuminate\Http\Request), 'show')

#12 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Route.php(203): Illuminate\Routing\ControllerDispatcher->dispatch(Object(Illuminate\Routing\Route), Object(Illuminate\Http\Request), '\\Module\\WenkuTo...', 'show')

#13 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Route.php(134): Illuminate\Routing\Route->runWithCustomDispatcher(Object(Illuminate\Http\Request))

#14 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Router.php(708): Illuminate\Routing\Route->run(Object(Illuminate\Http\Request))

#15 [internal function]: Illuminate\Routing\Router->Illuminate\Routing\{closure}(Object(Illuminate\Http\Request))

#16 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(139): call_user_func(Object(Closure), Object(Illuminate\Http\Request))

#17 /www/wwwroot/www.jmt.cn/module/Member/Middleware/WebAuthMiddleware.php(7): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#18 [internal function]: Module\Member\Middleware\WebAuthMiddleware->handle(Object(Illuminate\Http\Request), Object(Closure))

#19 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(124): call_user_func_array(Array, Array)

#20 /www/wwwroot/www.jmt.cn/vendor/modstart/modstart/src/App/Web/Middleware/BootstrapMiddleware.php(7): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#21 [internal function]: ModStart\App\Web\Middleware\BootstrapMiddleware->handle(Object(Illuminate\Http\Request), Object(Closure))

#22 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(124): call_user_func_array(Array, Array)

#23 [internal function]: Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#24 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(102): call_user_func(Object(Closure), Object(Illuminate\Http\Request))

#25 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Router.php(710): Illuminate\Pipeline\Pipeline->then(Object(Closure))

#26 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Router.php(674): Illuminate\Routing\Router->runRouteWithinStack(Object(Illuminate\Routing\Route), Object(Illuminate\Http\Request))

#27 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Routing/Router.php(635): Illuminate\Routing\Router->dispatchToRoute(Object(Illuminate\Http\Request))

#28 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(236): Illuminate\Routing\Router->dispatch(Object(Illuminate\Http\Request))

#29 [internal function]: Illuminate\Foundation\Http\Kernel->Illuminate\Foundation\Http\{closure}(Object(Illuminate\Http\Request))

#30 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(139): call_user_func(Object(Closure), Object(Illuminate\Http\Request))

#31 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(62): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#32 [internal function]: Illuminate\Session\Middleware\StartSession->handle(Object(Illuminate\Http\Request), Object(Closure))

#33 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(124): call_user_func_array(Array, Array)

#34 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php(37): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#35 [internal function]: Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse->handle(Object(Illuminate\Http\Request), Object(Closure))

#36 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(124): call_user_func_array(Array, Array)

#37 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php(59): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#38 [internal function]: Illuminate\Cookie\Middleware\EncryptCookies->handle(Object(Illuminate\Http\Request), Object(Closure))

#39 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(124): call_user_func_array(Array, Array)

#40 [internal function]: Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(Illuminate\Http\Request))

#41 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(102): call_user_func(Object(Closure), Object(Illuminate\Http\Request))

#42 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(122): Illuminate\Pipeline\Pipeline->then(Object(Closure))

#43 /www/wwwroot/www.jmt.cn/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(87): Illuminate\Foundation\Http\Kernel->sendRequestThroughRouter(Object(Illuminate\Http\Request))

#44 /www/wwwroot/www.jmt.cn/public/index.php(53): Illuminate\Foundation\Http\Kernel->handle(Object(Illuminate\Http\Request))

#45 {main}