more problems with IE

I wrote some javascript that works perfect in firefox but of course not the case it IE - IE 7 actually

IE gave me the error - null is null or not an abject

at point beyond this line this line - var select = document.getElementById("make_options");

if I comment out one line - the error goes to the next line

It's whenever I do anything to the select variable

I'm stuck - any help would be greatly appreciated

Here is the whole function

 // transform the JSON results into a drop down menu
  var select = document.getElementById("make_options");
  select.disabled=false;           // enable the dropdown
  select.onchange=getModels;       
  select.options[select.selectedIndex].disabled=true; // disable the 'Loading...' option
  select.options[select.selectedIndex].text="Select Make";
  
  for (var i = 0; i < json.feed.entry.length; ++i) {
    var entry = json.feed.entry[i];
      

  //isPreloading = false;

  
    // find the make entry
    if (entry.title.$t == "make(text)") {
      makeList = entry['gm$attribute']['gm$value']
      for (var j=0; j<makeList.length; ++j) {
        var option = document.createElement("option");
        make = makeList[j].$t
        option.appendChild(document.createTextNode(make));
        select.appendChild(option);
      }
      break;
    }
  }

Code (markup):

 

IE7 isn't finding an element with an ID of "make_options", apparently.

 

After a call to getElementById you should always check that you actually have a DOM element. eg:

var select = document.getElementById(id);
if(!select) // error handling here - throw an exception, popup an alert, or just return etc