AJAX :: AsyncFileUpload In CollapsiblePanel Is Not Working?

I have problem with AsyncFileUpload in CollapsiblePanel. In debug mode i have this error: "a._innerTB.style.width=a._inputFile.offsetWidth-107+"px"". I an begginer programmer and this is first time i see that kind of error. When AsyncFileUpload is outside the Panel or AsyncFileUpload everthing works perfect but i need this in AsyncFileUpload. Anyone know how to fix it? Or maybe there is another way to send file without reloading whole page (asp FIleUpload require reload)

<form id="form1" runat="server" enctype="multipart/form-data" method="post">
<ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
</ajaxToolkit:ToolkitScriptManager>
<div>
<asp:Panel ID="PanelHeader" runat="server">
<asp:Label ID="Label" runat="server" />
</asp:Panel>
<asp:Panel ID="PanelBody" runat="server">
Example
<ajaxToolkit:AsyncFileUpload runat="server" ID="AsyncFileUpload1" UploaderStyle="Modern"
UploadingBackColor="#CCFFFF" />
</asp:Panel>
<ajaxToolkit:CollapsiblePanelExtender ID="CollapsiblePanelExtender1" runat="server"
TargetControlID="PanelBody" CollapseControlID="PanelHeader" ExpandControlID="PanelHeader"
Collapsed="true" TextLabelID="Label" CollapsedText="Open" ExpandedText="Close"
CollapsedSize="0">
</ajaxToolkit:CollapsiblePanelExtender>
</div>
</form>