implement wxTreeCtrl::GetFocusedItem() for wxMSW too (see #10859)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61138 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -1354,6 +1354,11 @@ wxTreeItemId wxTreeCtrl::GetSelection() const
     wxCHECK_MSG( !HasFlag(wxTR_MULTIPLE), wxTreeItemId(),
                  wxT("this only works with single selection controls") );
 
+    return GetFocusedItem();
+}
+
+wxTreeItemId wxTreeCtrl::GetFocusedItem() const
+{
     return wxTreeItemId(TreeView_GetSelection(GetHwnd()));
 }