fix assert failure in LVN_KEYDOWN handler sometimes

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_2_BRANCH@7079 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/listctrl.cpp

@@ -1435,7 +1435,11 @@ bool wxListCtrl::MSWOnNotify(int idCtrl, WXLPARAM lParam, WXLPARAM *result)
                     event.m_code = wxCharCodeMSWToWX(wVKey);
                 }
 
-                event.m_item.m_data = GetItemData(lItem);
+                if ( lItem != -1 )
+                {
+                    // fill the client data field too
+                    event.m_item.m_data = GetItemData(lItem);
+                }
             }
             break;