xwayland: Use correct xwl_window lookup function in xwl_set_shape

In xwl_set_shape(), xwl_window_set_input_region() should be called only when the input shape of the toplevel window changes.

However, given that xwl_window_from_window() is going to walk the ancestor tree until it finds an xwl_window, that lookup function cannot be used. Instead, xwl_window_get() should be used. It's going to return a valid xwl_window object iff the specified window has one associated with it.

Signed-off-by: Vlad Zahorodnii vlad.zahorodnii@kde.org