Please set the 'value' with a non empty value such as -1, or try to put this code to the page to fix this issue.
<script>
$.extend($.easyui, {
indexOfArray: function(a, o, id){
for(var i=0,len=a.length; i<len; i++){
if (id == undefined){
if (a[i] == o){return i;}
} else {
if (String(a[i][o]) == String(id)){return i;}
}
}
return -1;
}
})
</script>