ASSERT INFO:
./src/gtk/window.cpp(3446): assert "(m_widget != NULL)" failed in DoAddChild(): invalid window

BACKTRACE:
[1] wxWindow::DoAddChild(wxWindow*)
[2] wxWindow::Create(wxWindow*, int, wxPoint const&, wxSize const&, long, wxString const&)
[3] wxPanelBase::Create(wxWindow*, int, wxPoint const&, wxSize const&, long, wxString const&)
[4] wxPanel::wxPanel(wxWindow*, int, wxPoint const&, wxSize const&, long, wxString const&)
[5] java_wxpanel::java_wxpanel(java_wxwindow*, int, int, int, int, int, long, std::string)
[6] Java_wx_JNI_wxpanel_1moduleJNI_new_1java_1wxpanel
[7] clone