The Message TVM_EXPAND is captured in treeview_notify, then passes
g_pChildWnd->hTreeWnd on to OnTreeExpanding which hasn't been
initialized yet.  The function get_last_key is already called after
the hTreeWnd has been assigned to select the previous selected
item (if it exists).
Signed-off-by: Alistair Leslie-Hughes <leslie_alistair@hotmail.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>