When I return a HEAD 200 to a Jquery ajax call. I got: JSON Parse error: Unexpected EOF. The whole error looks like this:

[[Image(http://i.imgur.com/xTYaT.png)]]

pass back an empty JSON then it is OK

my ajax call looks like this:

$(function(){
  $("#login-form").submit(function(){
    var form_values = $(this).serializeArray();
    $.ajax({
      url: "/login.json",
      type: "post",
      data: form_values,
      success: function(){
        window.location.href = "/";
      },

      error: function(jqXHR, textStatus, errorThrown){
        console.log(textStatus);
        console.log(jqXHR);
        console.log(errorThrown);
      }
    }
    );
    return false;
  })
}
);