wicd-curses crashes on trying to select wired encryption type

This bug was introduced (by me >.>) in version 1.7.1, as part of the wired encryption feature.

Steps to reproduce:
1. Open up wicd-curses, and go to the configuration menu for the wired interface
2. Enable encryption
3. Try to select the encryption type from the menu
4. Program crashes

This can be worked around by not trying to change the encryption type on the wired network (there is only one type available currently anyway).

Error:
~ $ wicd-curses

Traceback (most recent call last):
  File "/usr/share/wicd/curses/wicd-curses.py", line 921, in call_update_ui
    self.update_ui(True)
  File "/usr/share/wicd/curses/wicd-curses.py", line 89, in wrapper
    return func(*args, **kargs)
  File "/usr/share/wicd/curses/wicd-curses.py", line 932, in update_ui
    self.handle_keys(input_data[1])
  File "/usr/share/wicd/curses/wicd-curses.py", line 907, in handle_keys
    k = self.frame.keypress(self.size,k)
  File "/usr/lib/python2.7/site-packages/urwid/container.py", line 641, in keypress
    return self.body.keypress( (maxcol, remaining), key )
  File "/usr/lib/python2.7/site-packages/urwid/container.py", line 641, in keypress
    return self.body.keypress( (maxcol, remaining), key )
  File "/usr/lib/python2.7/site-packages/urwid/listbox.py", line 766, in keypress
    key = focus_widget.keypress((maxcol,),key)
  File "/usr/share/wicd/curses/curses_misc.py", line 405, in keypress
    raise ComboBoxException('ComboBox must be built before use!')
curses_misc.ComboBoxException: ComboBox must be built before use!