fix for the crash when many listctrl items change state

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@12956 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/listctrl.cpp

@@ -978,8 +978,10 @@ bool wxSelectionStore::SelectRange(size_t itemFrom, size_t itemTo,
                             // stop counting (see comment below)
                             itemsChanged = NULL;
                         }
-
-                        itemsChanged->Add(m_itemsSel[i]);
+                        else
+                        {
+                            itemsChanged->Add(m_itemsSel[i]);
+                        }
                     }
 
                     m_itemsSel.RemoveAt(i);