detect and report errors in XRC specification of grid sizers

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@59572 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/xrc/xh_sizer.h

@@ -47,6 +47,7 @@ private:
     wxGridBagSizer* Handle_wxGridBagSizer();
     wxSizer*  Handle_wxWrapSizer();
 
+    bool ValidateGridSizerChildren();
     void SetGrowables(wxFlexGridSizer* fsizer, const wxChar* param, bool rows);
     wxGBPosition GetGBPos(const wxString& param);
     wxGBSpan GetGBSpan(const wxString& param);