Handle case when there is no worker any more for a given scheduling node

src/sched_policies/node_sched.c

@@ -575,9 +575,10 @@ static void set_properties(struct starpu_sched_node * node)
 {
 	STARPU_ASSERT(node);
 	node->properties = 0;
-	STARPU_ASSERT(starpu_bitmap_cardinal(node->workers_in_ctx) > 0);
 
 	int worker = starpu_bitmap_first(node->workers_in_ctx);
+	if (worker == -1)
+		return;
 	uint32_t first_worker = _starpu_get_worker_struct(worker)->worker_mask;
 	unsigned first_memory_node = _starpu_get_worker_struct(worker)->memory_node;
 	int is_homogeneous = 1;