Fix for the user function base class UF_window class - it wasn't closing properly.
This was identified by Michael at https://mail.gna.org/public/relax-devel/2010-12/msg00020.html.
The wx.Frame object was being used when it should have been wx.Dialog.
Authored by: bugman 2010-12-09
Parent: [r11751]
Child: [r11753]
