`body` may be undefined, and it would crash
`body` may be undefined, and it would crash

Add this condition, it will be like this:
JSON.parse error: SyntaxError: Unexpected token < in JSON at position 0
    at JSON.parse (<anonymous>)
    at ServerResponse.res.end (xxx\node_modules\node-http-proxy-json\index.js:111:19)
    at IncomingMessage.onend (_stream_readable.js:598:10)
    at Object.onceWrapper (events.js:314:30)
    at emitNone (events.js:110:20)
    at IncomingMessage.emit (events.js:207:7)
    at endReadableNT (_stream_readable.js:1059:12)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickCallback (internal/process/next_tick.js:180:9)
No response!

At least, it won't crash!
langjt/node-http-proxy-json