Warning: Undefined array key "sitemap.xml" in /var/task/user/router.php on line 16

Fatal error: Uncaught TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, no array or string given in /var/task/user/router.php:18 Stack trace: #0 /var/task/user/index.php(46): dispatch('sitemap.xml') #1 /var/task/user/api/index.php(2): require('/var/task/user/...') #2 {main} thrown in /var/task/user/router.php on line 18