Some error when i use xtype : 'filefield'

[Maskca]

Hey, i use xtype : 'filefield' for uploding images, and when i click on upload button i get some error:
In Chrome i get:

Uncaught Ext.JSON.decode(): You're trying to decode an invalid JSON String: ext-all.js:38
Ext.Error.Ext.extend.statics.raise ext-all.js:38
me.decode ext-all.js:38
Ext.define.handleResponse ext-all.js:38
Ext.define.processResponse ext-all.js:38
Ext.define.onSuccess ext-all.js:38
Ext.apply.callback ext-all.js:38
Ext.define.onUploadComplete ext-all.js:38
(anonymous function) ext-all.js:38
(anonymous function)
g


In Firefox:

TypeError: a is undefined

...f(p==k){if(a+E+l.width>(O>=0?u.x+u.width-b:b-u.x)){p=M}}else{if(a+E>l.width){p=k...

ext-all.js


TypeError: a is undefined


But image uploading successfuly

Can you help me to fix this error

[Akatum]

Solution is described in documentation:
http://docs.sencha.com/ext-js/4-1/#!...thod-hasUpload