javascript - ExtJS ComboBox Uncaught TypeError: Cannot read property 'scrollIntoView' of null -

my ext version 4.07.

i create combobox , want store data json file.

var combo = ext.create(ext.form.combobox, {                 editable: false,                 fieldlabel: 'choose format',                 store: ext.create(ext.data.store, {                     autoload: true,                     fields: ['format', 'dimension'],                     proxy: {                         type: 'ajax',                         url: 'jsonurl', // has masked here                         reader: {                             type: 'json',                             root: 'formats'                         }                     },                     listeners: {                       load: function(me) {                         var defaultvalue = me.getat(0).data.dimension;                         combo.select(defaultvalue);                       }                   }                 }),                 displayfield: 'dimension',                 valuefield: 'format',                 querymode: 'local',             }); 

in case, did ajax call , loaded data when click combobox chrome developer tool console show error message: "uncaught typeerror: cannot read property 'scrollintoview' of null"

in firefox console show message: "typeerror: ext.fly(...) null ext.fly(child, '_scrollchildintoview').scrollintoview(this, hscroll);"

is there ideas fix problem?

thanks lot!

update:

i got problem. wrote load event , want set default value combobox set incorrect reference cause error message.

load: function(me) {   //var defaultvalue = me.getat(0).data.dimension; //incorrect   var defaultvalue = me.getat(0); //correct   preferformat.select(defaultvalue); }