[Bug] AttributeError: 'NoneType' object has no attribute 'id'

[smartcatboy]

AttributeError: 'NoneType' object has no attribute 'id'
  File "huey/api.py", line 379, in _execute
    task_value = task.execute()
  File "huey/api.py", line 772, in execute
    return func(*args, **kwargs)
  File "tasks/traffic.py", line 20, in traffic_server_runner
    finished_callback=iptables_finished_handler(server.id),

Unhandled exception in task 89a96969-0e37-4391-9fa1-a3a5be1a742d.

这个问题应该是由于删除 server 后，队列中还有 ddns 任务正在执行造成的。