Gmail – Sending an email with just an attachment with script

Here is my script for forwarding emails to another inbox. However, now I want to only send emails that are unread with attachments to one email and then if no attachment to a different email. Can someone help me? I believe I would have to put something in the gmailapp.search about attachments, but I can't figure it out. I'm very green around the ears with this.

function AutoForward() {

  //send response email
  var threads = GmailApp.search("to:br@345.com is:unread,is:attachment=true");
  var subject = "";
  var msg = "";
  var c = 0; // will be used to count the messages in each thread
  var t = "";
  var attachment = "";
  var forwarded = "";

  for (var i = 0; i < threads.length; i++) { 
    // I set 'i' to 3 so that you can test the function on your 3 most recent unread emails.
    // to use it on all your unread email, remove the 3 and remove the /* and */ signs.

t = threads[i]; // I wanted to avoid repetition of "threads[i]" for the next 2 lines haha
c = t.getMessageCount() - 1;
msg = t.getMessages()[c];
 
forwarded = msg.getBody(); // that is the body of the message we are forwarding.

subject = msg.getSubject();
attachment = msg.getAttachments();

msg.forward("a@1234.com", {
  replyTo: "mail@abc.com",
  
  //htmlBody: "" //adds your message to the body
    //+
    //"<div style='text-align: center;'>---------- Forwarded message ----------</div><br>" + forwarded, //centers
  attachments: attachment
});
  t.markRead(); // mark each forwarded thread as read, one by one
  }
}