Missing a test of Arguments Optional

Tell us what’s happening:
Describe your issue in detail here.
Hello , could anyone tell me what’s wrong with my code , i miss the following test ( addTogether("https://www.youtube.com/watch?v=dQw4w9WgXcQ") should return undefined .)
thank you in advance.

   **Your code so far**
function addTogether() {
 let arg=Array.from(arguments)
   return x=>addTogether(arg[0],x)
if(arg.some(element=>typeof element!=='number')){
  return undefined
return arg[0]+arg[1]

   **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/ Safari/537.36

Challenge: Arguments Optional

Link to the challenge:

that will be a recursion, because you are calling the same function inside itself, but you are not supposed to do it, you have to return a new function

you have to check for invalid numbers here too

Or you can change the order of the if statements.