我已經在 Repl.it 網站上解決了這個問題，但是當我在 LeetCode 上提交代碼時，它給出了一個 typeError，我將把它粘貼在這里：Line 29 in solution.js         throw new TypeError(__serialize__(ret) + " is not valid value for the expected return type ListNode");         ^TypeError: [] is not valid value for the expected return type ListNodeLine 29: Char 20 in solution.js (Object.<anonymous>)Line 16: Char 8 in runner.js (Object.runner)Line 13: Char 26 in solution.js (Object.<anonymous>)Line 1200: Char 30 in loader.js (Module._compile)Line 1220: Char 10 in loader.js (Object.Module._extensions..js)Line 1049: Char 32 in loader.js (Module.load)Line 937: Char 14 in loader.js (Function.Module._load)at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)Line 17: Char 47 in run_main_module.js這是代碼：var mergeTwoLists = function(l1, l2) {  let i = 0, j = 0;  var out = [];  while(i < l1.length || j < l2.length) {    if(j == l2.length || i < l1.length && l1[i] < l2[j]) {      out.push(l1[i++]);    } else {      out.push(l2[j++]);    }  }  return out;};我真的不知道問題出在哪里......如果有人可以幫助我將不勝感激