Javascript error on page refresh

Question

i am using an fckeditor outside the update panel and rest other things are inside update panel but on refreshing the page it is throwing an exception

function WebForm_OnSubmit() {
null;(function()
{
    var editor = FCKeditorAPI.GetInstance('ctl00_ContentPlaceHolder1_FCKeditorSelfDocument');
    if (editor)
        editor.UpdateLinkedField();
})();

that FCKeditorAPI is not defined what am i doing wrong