Unhandled Promise Rejection when writing to a closed/unavailable socket

[joebwan]

If the AGI socket closes for some reason ding-dong (context.js) will throw an unhandled promise rejection error.

See line 117 of context.js in master branch.

UnhandledPromiseRejectionWarning: Error [ERR_STREAM_WRITE_AFTER_END]: write after end
at writeAfterEnd (_stream_writable.js:266:14)
at Socket.Writable.write (_stream_writable.js:315:5)
at Readable.write (node_modules/readable-stream/lib/_stream_readable.js:855:33)
at Context.send (lib/context.js:117:15)
at lib/context.js:130:10
at new Promise ()
at Context.sendCommand (lib/context.js:129:10)

[joebwan]

These errors do not get logged to STDOUT, but instead get bubbled up to node.js for logging to STDERR.