JS error is thrown when opening a tool in Lightweight and ShowAjaxLoadingPanel="true".

Error message:
Uncaught TypeError: Cannot set property 'id' of undefined
     at Telerik.Web.UI.RadImageEditor._showAjaxLoadingPanel


Steps to reproduce:
1. Run the following code
            <telerik:RadImageEditor ID="RadImageEditor1" ShowAjaxLoadingPanel="true" runat="server" RenderMode="Lightweight" ImageUrl="~/Images/Summdary.jpg">
            </telerik:RadImageEditor>

2. Open the "Crop" dialog

Result: A JS error is thrown.