Why error ?

[ENDUNDER]

function promptuser()
  local answer = gg.prompt("do you want to proceed?", "yes")
  if answer == "yes" then
    gg.alert("proceeding...")
  else if answer == "no" then
    gg.alert("aborting...")
    gg.skipcurrentscript()   -- exit the current script
  else
    gg.alert("please enter 'yes' or 'no'")
    promptuser()  
  end
end

[HEROGAMEOfficial]

https://gameguardian.net/help/classgg.html