error thrown from btnEl

[ngzax]

when i try to use this component, i receive the following error:

this.btnEl is undefined

the error is starts here:
anonymous(Object dom=td#ext-gen49.x-toolbar-cell id=ext-gen49, Object name=position)
Exporter-all.js (line 189)

I am trying to export a GroupingStore using the following:

new Ext.ux.Exporter.Button({component: xref_grid})

I have tried to debug what is going on but don't know enough js to be useful.
Any help is greatly appreciated.