Don't Set Thread References to None

[dvonthenen]

Proposed changes

Addresses issue: #370

I believe this is similar to this issue fixed in PR #366. The threads should have already exited (because of the join and gather) but in the event that hasn't happened yet, this keeps the thread references around until a reconnect has happened (ie they will be replaced with new thread references).

Also, found in testing an additional place where an exception can be thrown on a successful exit.

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• New feature (non-breaking change which adds functionality)
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Checklist

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Further comments

Tested AsyncLive and Live Clients for all examples.