Server EventMachine can segfault on ruby exceptions or watchdog aborts

[SpComb]

The server uses EventMachine 1.2.3, which can segfault during cleanup after a callback raises an exception and EM aborts: eventmachine/eventmachine#765

This can happen if some WebsocketBackend function raises an exception, or if the new #2139 Watchdog aborts the EM thread (only during EM::Connection#unbind callbacks, or any EM callbacks..?).

This also seems to hide the original exception that was raised.

It would seem that these puma worker segfaults are mostly harmless, as puma will still restart the worker: #2139 (comment)