Tor tries to kill nonexistent proxy PID on second SIGINT

This is what 180-pluggable-transport.txt says about proxies and SIGINT:

Proxies should respond to a single INT signal by closing their listener ports and not accepting any new connections, but keeping all connections open, then terminating when connections are all closed. Proxies should respond to a second INT signal by shutting down cleanly.

I implemented the websocket-server transport to work as specified: https://gitweb.torproject.org/flashproxy.git/blob/c23caf1f71f8281319cadf55002723dbcd333905:/websocket-transport/websocket-server.go#l238 I noticed unexpected behavior when the proxy receives a SIGINT, and doesn't have any open connection, and so exits immediately without waiting for a second SIGINT. The parent tor process tries to kill a nonexistent PID:

^CApr 19 17:58:59.000 [notice] Interrupt: we have stopped accepting new connections, and will shut down in 30 seconds. Interrupt again to exit now.
^CApr 19 17:59:05.000 [notice] SIGINT received a second time; exiting now.
Apr 19 17:59:05.000 [notice] Failed to terminate process with PID '18277' ('No such process').

The PID might have been reclaimed in the meantime, and tor could be killing an unrelated process.

(Originally from https://lists.torproject.org/pipermail/tor-dev/2013-April/004679.html.)