Unhandled 'error' event and server crash if attempted webrtc connection to proxy server

[4c656554]

This error occurs if you set the DEFAULT_WEBRTC_BOOTSTRAP in ```dat-sdk`` to a hyperswarm-web proxy server. This would be a mistake, but perhaps it could be used to deliberately crash the hyperswarm-web server.

events.js:291
      throw er; // Unhandled 'error' event
      ^

Error: Decoded message is not valid
    at Object.decode (/usr/lib/node_modules/hyperswarm-web/node_modules/hyperswarm-proxy/messages.js:117:28)
    at Client._write (/usr/lib/node_modules/hyperswarm-web/node_modules/hyperswarm-proxy/index.js:109:34)
    at doWrite (_stream_writable.js:403:12)
    at writeOrBuffer (_stream_writable.js:387:5)
    at Client.Writable.write (_stream_writable.js:318:11)
    at Decoder.ondata (/usr/lib/node_modules/hyperswarm-web/node_modules/readable-stream/lib/_stream_readable.js:681:20)
    at Decoder.emit (events.js:314:20)
    at addChunk (/usr/lib/node_modules/hyperswarm-web/node_modules/readable-stream/lib/_stream_readable.js:298:12)
    at readableAddChunk (/usr/lib/node_modules/hyperswarm-web/node_modules/readable-stream/lib/_stream_readable.js:280:11)
    at Decoder.Readable.push (/usr/lib/node_modules/hyperswarm-web/node_modules/readable-stream/lib/_stream_readable.js:241:10)
Emitted 'error' event on HyperswarmServer instance at:
    at Client.<anonymous> (/usr/lib/node_modules/hyperswarm-web/node_modules/hyperswarm-proxy/server.js:52:14)
    at Object.onceWrapper (events.js:421:26)
    at Client.emit (events.js:326:22)
    at errorOrDestroy (internal/streams/destroy.js:108:12)
    at onwriteError (_stream_writable.js:418:5)
    at onwrite (_stream_writable.js:445:5)
    at Client._write (/usr/lib/node_modules/hyperswarm-web/node_modules/hyperswarm-proxy/index.js:120:7)
    at doWrite (_stream_writable.js:403:12)
    at writeOrBuffer (_stream_writable.js:387:5)
    at Client.Writable.write (_stream_writable.js:318:11)