fix: iteration node in parallel mode token count error (#11539)

Co-authored-by: Novice Lee <novicelee@NoviPro.local>

api/core/workflow/nodes/iteration/iteration_node.py

                     future.add_done_callback(thread_pool.task_done_callback)
                     futures.append(future)
                 succeeded_count = 0
-                empty_count = 0
                 while True:
                     try:
                         event = q.get(timeout=1)
                 parallel_mode_run_id=parallel_mode_run_id,
             ):
                 q.put(event)
+            graph_engine.graph_runtime_state.total_tokens += graph_engine_copy.graph_runtime_state.total_tokens