Stop client_listener from raising a KeyError when receiving a client_stopped message from unknown worker

[BirdLearn]

fix: client_listener will raise an KeyError error when received a client_stopped message from an unknown worker.

[cyberw]

We need to at least log a warning when it happens. Also, to avoid the deep nesting, can you reverse the if-statement to be:

if not msg.node_id in self.clients:
    continue

[BirdLearn]

We need to at least log a warning when it happens. Also, to avoid the deep nesting, can you reverse the if-statement to be:

if not msg.node_id in self.clients:
    continue

When I modified the code, I found that the same judgment was made on other conditional branches, such as "heartbeat" and "quit", so, in order to keep the code style consistent, I made the same code modification.

In addition, I found that after processing the message, there is a check_stopped() call, if I use "continue " to skip this loop, it will not execute to check_stopped(), I am worried about other side effects.

[cyberw]

Not calling check_stopped in this case should be fine (this is only relevant if a worker has actually stopped, so skipping it is a).

In this case I think readability (and minimizing the changes to maintain git blame history) is more important than consistency.

But the logging is the most important.