Fix history not showing (RT-2341)

This PR fixes the unsafe object reference in jsonrewriter that causes the following bug:

https://ripplelabs.atlassian.net/browse/RT-2341

Beyond fixing this particular bug, this pull request aims to fix the entire class of problems by adding a try/catch block such that any future issue with transaction rewriting will only prevent that particular transaction from rendering correctly, it will not prevent the entire list from showing up.

The new code will also notify us about any transactions that fail to parse via Mixpanel.