Your error is due to the way you log your output:
var text1 = document.getElementById("divid").innerHTML;
document.getElementById("divid").innerHTML = text1 + [...]
Since 'divid' contains the FilteringSelect dijit markup, setting again divid.innerHTML overwrites the existing DOM and messes up the existing FilteringSelect dijit instance. In general, you should not modify the DOM of a dijit instance. Just add an empty span element to your markup to log your values:
<div id="divid">
Select a State : <input id="stateSelect">
<span id="buffer"></span>
</div>
and onChange becomes :
onChange: function(value){
var text1 = document.getElementById("buffer").innerHTML;
document.getElementById("buffer").innerHTML = text1 + [...]
}