check option value before using it, closes #196

mitterlib/ui/ui_pygtk.py

@@ -1049,7 +1049,9 @@ class Interface(object):
                     pass
 
                 new_field = gtk.Entry()
+                if option_value:
                     new_field.set_text(option_value)
+
                 # Ony "str" and "passwd" are valid type and both use Entry()
                 if option['type'] == 'passwd':
                     new_field.set_visibility(False)