Problem With "Auto Fit All Columns" in List Grid's Header Context Menu

Hi,
I am using smart Gwt-3.x pro,
In my application I have overridden List Grid's Header Context Menu for the purpose of "Simple Filter" and "Reset Filter".
When am clicking "Auto Fit All Columns"(From Header Context Menu" I am getting the exception.
Please find the Exception details from the attachment.
Please give me a solution for "Auto fit all columns" functionality.


Thanks in advance.

Attached Images

autoFitAllColsImg.jpg (131.8 KB)