WindowManager: make render order workaround safer

Include the window's generation number in the hash rather than only
the memory address.

 river/WindowManager.zig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/river/WindowManager.zig b/river/WindowManager.zig
index 553c0b3..7d1a16a 100644
--- a/river/WindowManager.zig
+++ b/river/WindowManager.zig
@@ -463,7 +463,7 @@ fn renderFinish(wm: *WindowManager) void {
         while (it.next()) |node| {
             switch (node.get()) {
                 .window => |window| {
-                    hash.update(@ptrCast(&window));
+                    hash.update(@ptrCast(&window.ref));
                     hash.update(&.{@intFromBool(window.wm_requested.fullscreen != null)});
                 },
                 .shell_surface => |shell_surface| {