Issues with grid appearance field picker

Hey,

so I do not know if it is really a bug... it also appears in your showcase... simply try to move the pop up with the mouse or click on the header of the window... the pop Up disappears. Shouldn't this window be a modal window?

Showcase:
http://www.smartclient.com/smartgwt/showcase/#grid_appearance_field_picker

Or is there a simple way to make it modal and to make the background outside of this window darker? So that you can see that it is a modal window.