reset m_selection in DeleteAllPages() (patch 1922215); some cleanup of DoRemovePage() in trunk

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@53045 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/choicbkg.cpp

@@ -291,6 +291,7 @@ wxWindow *wxChoicebook::DoRemovePage(size_t page)
 
 bool wxChoicebook::DeleteAllPages()
 {
+    m_selection = wxNOT_FOUND;
     GetChoiceCtrl()->Clear();
     return wxBookCtrlBase::DeleteAllPages();
 }