message: fix(GUI): properly pass error object to "Flash error" event
  Simply running `_.merge` on an Error object results in an empty plain
  object `{}` being sent to Mixpanel/Sentry.
diff: @@ -25,6 +25,7 @@ const _ = require('lodash');
  const childWriter = require('../../child-writer');
  const settings = require('../models/settings');
  const flashState = require('../../shared/models/flash-state');
  +const errors = require('../../shared/errors');
  const windowProgress = require('../os/window-progress');
  const analytics = require('../modules/analytics');
  @@ -134,7 +135,7 @@ imageWriter.service('ImageWriterService', function($q, $rootScope) {
  analytics.logEvent('Out of space', analyticsData);
  } else {
  analytics.logEvent('Flash error', _.merge({
  - error
  + error: errors.toJSON(error)
  }, analyticsData));
  }
  