jQuery Grid Plugin - jqGrid

I have a question to address the issue regarding unbinding unload event handler bound to window object in jqGrid.

In my application pages consists of main part and its contents, which will be dynamically loaded via AJAX as followings.

 1. Load Main part via Ajax.

     (In main js are implemented to load its contents.)

 2. Load its contents part via Ajax.

 3. User click a bottun.

 4. Refresh not whole but contents part.

If user wants to render contents part which consists of jqGrid and the contents rendered already has jqGrid, unload event handler, which was bound in rendering former jqGrid, will be orphan.

In my application jqGrid is not reused but created as contents part is rendering.

How can I safely unbind its event handler ?

FYI: Binding unload event handler to $(window) is done line 2544 in jquery.jqGrid.src.js, version 4.3.1.

Regards.