Don't crash in wxControl::GetLabel when getting the label

  Don't crash in wxControl::GetLabel when getting the label
fails (perhaps because the widget is not realized?).
  Correct wxRTTI information for wxFrame: it derives from
wxTopLevelWindow, not wxWindow.
  Don't try setting Widget size to 0, because it will fail: set
it to 1 instead which is exactly as sensible, but does not crash.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@23288 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775