wrap websocket messages json parsing in a try/catch

[patrickdbakke]

Summary

Fixes zen crashing when you repeatedly / rapidly save the same file.

Changes

Wrap json.parse() in a try catch when receiving websocket messages.

Underlying error:

ConsoleMessage {}
- 00ab756aeb8e0ba99e9f
undefined:1
- 00ab756aeb8e0ba99e9f
 ^

SyntaxError: Unexpected token   in JSON at position 1
    at JSON.parse (<anonymous>)
    at register (/Users/patrickbakke/www/desktop/node_modules/@superhuman/zen/build/cli.js:3097:30)
    at ChromeTab.onMessageAdded (/Users/patrickbakke/www/desktop/node_modules/@superhuman/zen/build/cli.js:3104:9)
    at /Users/patrickbakke/www/desktop/node_modules/@superhuman/zen/build/cli.js:2976:16
    at /Users/patrickbakke/www/desktop/node_modules/puppeteer/lib/cjs/vendor/mitt/src/index.js:51:68
    at Array.map (<anonymous>)
    at /Users/patrickbakke/www/desktop/node_modules/@superhuman/zen/node_modules/sugar/enumerable/internal/wrapNativeArrayMethod.js:12:21
    at Array.staticFn.instance (/Users/patrickbakke/www/desktop/node_modules/@superhuman/zen/node_modules/sugar/common/internal/fixArgumentLength.js:10:12)
...

[zindlerb]

Lgtm!