adjust for https://github.com/varnishcache/varnish-cache/pull/3011

src/vmod_topvar.c

@@ -78,10 +78,17 @@ static void *
 state_l(VRT_CTX, void *v, size_t sz)
 {
 	struct vmod_priv *t;
+	struct ws *ws;
 
 	top_common(ctx, t, v);
 
-	t->priv = WS_Alloc(ctx->req->topreq->ws, sz);
+	if (ctx->req->top)
+		ws = ctx->req->top->topreq->ws;
+	else
+		ws = ctx->req->ws;
+
+	t->priv = WS_Alloc(ws, sz);
+
 	if (t->priv == NULL) {
 		VRT_fail(ctx, "out of workspace");
 		return (NULL);