crash on uplink error + client disconnect

[rlidwka]

Rarely happens, but smells like a bug:

 http  --> ERR, req: 'GET http://registry.npmjs.org/multiparty/-/multiparty-2.2.0.tgz', error: ESOCKETTIMEDOUT
 warn  --> host registry.npmjs.org is now offline
 error --- unexpected error: ESOCKETTIMEDOUT
Error: ESOCKETTIMEDOUT
    at ClientRequest.<anonymous> (/tmp/sinopia/node_modules/request/request.js:688:19)
    at ClientRequest.g (events.js:175:14)
    at ClientRequest.EventEmitter.emit (events.js:92:17)
    at Socket.emitTimeout (http.js:1797:10)
    at Socket.g (events.js:175:14)
    at Socket.EventEmitter.emit (events.js:92:17)
    at Socket._onTimeout (net.js:327:8)
    at Timer.unrefTimeout [as ontimeout] (timers.js:412:13)
 fatal --- uncaught exception, please report this
Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (http.js:691:11)
    at ServerResponse.res.setHeader (/tmp/sinopia/node_modules/express/node_modules/connect/lib/patch.js:63:22)
    at ServerResponse.res.set.res.header (/tmp/sinopia/node_modules/express/lib/response.js:527:10)
    at ServerResponse.res.send (/tmp/sinopia/lib/middleware.js:131:8)
    at ServerResponse.res.report_error (/tmp/sinopia/lib/index.js:77:10)
    at ReadTarball.<anonymous> (/tmp/sinopia/lib/index.js:165:15)
    at ReadTarball.EventEmitter.emit (events.js:117:20)
    at ReadTarball.<anonymous> (/tmp/sinopia/lib/storage.js:258:12)
    at ReadTarball.EventEmitter.emit (events.js:117:20)
    at Request.<anonymous> (/tmp/sinopia/lib/up-storage.js:271:10)