我有一个使用超薄框架的在线应用程序。该网站似乎工作正常，但当我检查错误日志时，我得到了以下内容。
[Mon Apr 17 13:26:45.349695 2017] [:error] [pid 30816] [client xx.xxx.xx.133:39856] PHP Notice: Undefined offset: 0 in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 80
[Mon Apr 17 13:26:45.349755 2017] [:error] [pid 30816] [client xx.xxx.xx.133:39856] PHP Notice: Undefined variable: output in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 61
[Wed Apr 19 22:14:32.271000 2017] [:error] [pid 13509] [client xx.xxx.xx.251:59585] PHP Notice: Undefined offset: 0 in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 80
[Wed Apr 19 22:14:32.271546 2017] [:error] [pid 13509] [client xx.xxx.xx.251:59585] PHP Notice: Undefined variable: output in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 61
[Thu Apr 20 15:07:51.858254 2017] [:error] [pid 16996] [client xx.xxx.xx.61:37389] PHP Notice: Undefined offset: 0 in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 80
[Thu Apr 20 15:07:51.858844 2017] [:error] [pid 16996] [client xx.xxx.xx.61:37389] PHP Notice: Undefined variable: output in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 61
[Fri Apr 21 10:27:05.650765 2017] [:error] [pid 20800] [client xx.xxx.xx.224:49737] PHP Notice: Undefined offset: 0 in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 80
[Fri Apr 21 10:27:05.651262 2017] [:error] [pid 20800] [client xx.xxx.xx.224:49737] PHP Notice: Undefined variable: output in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 61
[Sat Apr 22 14:27:29.531275 2017] [:error] [pid 25129] [client xx.xxx.xx.62:59309] PHP Notice: Undefined offset: 0 in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 80
[Sat Apr 22 14:27:29.531323 2017] [:error] [pid 25129] [client xx.xxx.xx.62:59309] PHP Notice: Undefined variable: output in /var/www/Sites/appName/vendor/slim/slim/Slim/Handlers/NotFound.php on line 61
我自己试图对此进行诊断，但根本没有达到目的。有人能指出我正确的方向试图找出这两个错误的原因吗？