#244 Crash when adding blank wxPanel to blank wxNotebook

[Jonathan E. Magen]

To reproduce crash:

1. Start boa-constructor
2. Select new wxFrame
3. Open frame designer
4. Add wxNotebook to frame
5. Attempt to add wxPanel anywhere inside wxNotebook

Bug discovered using:
Mepis Linux 3.3
Kernel version: 26.10
Python: 2.3.5
wxPython package installed: libwxgtk2.4-python
Boa-constructor version: 0.3.0