[XXE] Should xxe-config: work for an icon?

[Bill Fenner]

When I use the following in my config file:

   <button icon="xxe-config:common/icons2/emphasis_menu.gif"
            toolTip="Convert to emphasis (spanx)">

I get a dialog about an illegal icon value (the same as if I have a
nonexistent file).  Should xxe-config: work inside a toolBar button
icon attribute?

Thanks,
  Bill