Avoid double deletion of notebook page windows, don't call DestroyChildren in

~wxAuiMDIClientWindow.  Also skip the hide page optimization when destroying 
the notebook. 

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@48924 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/aui/auibook.cpp

@@ -3259,7 +3259,8 @@ bool wxAuiNotebook::DeletePage(size_t page_idx)
 
     // hide the window in advance, as this will
     // prevent flicker
-    ShowWnd(wnd, false);
+	if ( !IsBeingDeleted() )
+        ShowWnd(wnd, false);
 
     if (!RemovePage(page_idx))
         return false;

src/aui/tabmdi.cpp

@@ -716,7 +716,6 @@ wxAuiMDIClientWindow::wxAuiMDIClientWindow(wxAuiMDIParentFrame* parent, long sty
 
 wxAuiMDIClientWindow::~wxAuiMDIClientWindow()
 {
-    DestroyChildren();
 }
 
 bool wxAuiMDIClientWindow::CreateClient(wxAuiMDIParentFrame* parent, long style)