Avoid a crash due to OnSize being called before initialisation

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@47330 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/grid.cpp

@@ -4188,6 +4188,7 @@ bool wxGrid::Create(wxWindow *parent, wxWindowID id,
 
     Create();
     SetInitialSize(size);
+    CalcDimensions();
 
     return true;
 }
@@ -6905,8 +6906,11 @@ void wxGrid::Refresh(bool eraseb, const wxRect* rect)
 
 void wxGrid::OnSize( wxSizeEvent& WXUNUSED(event) )
 {
+    if (m_targetWindow != this) // check whether initialisation has been done
+    {
         // update our children window positions and scrollbars
         CalcDimensions();
+    }
 }
 
 void wxGrid::OnKeyDown( wxKeyEvent& event )