title: EditorGUILayout.Popup option is not changing
body: <p>using this simple code I'm showing a dropdown</p>
  
  <pre><code> int selected = 0;
              ///*
              string[] options = new string[]
              {
                  "Start With", "End With", "Contains", 
              };
  
              //criteria = EditorGUILayout.Popup("Search Criteria", 2, options);
              //*/
              criteria = EditorGUILayout.Popup("Awesome Drop down:",  selected, options, EditorStyles.popup);
  </code></pre>
  
  <p>it showing dropdown with option perfectly but the problem is option is not changing when I try to select another option? what is missing?</p>